High power density and/or linearity transistors Number:7,161,194 from the United States Patent and Trademark Office (PTO) owispatent Field effect transistors having a power density of greater than 25 W/mm when operated at a frequency of at least 4 GHz are provided. The power density may be at least 30 W/mm when operated at 4 GHz. The power density of at least 30 W/mm may be provided at a drain voltage of 120 V. Transistors with a power density of at least 30 W/mm when operated at 8 GHz are also provided. The power density of at least 30 W/mm may be provided at a drain voltage of 120 V. Field effect transistors having a power density of greater than 20 W/mm when operated at a frequency of at least 10 GHz are also provided. Field effect transistors having a power density of at least 2.5 W/mm and a two tone linearity of at least -30 dBc of third order intermodulation distortion at a center frequency of at least 4 GHz and a power added efficiency (PAE) of at least 40% are also provided.<H transistors, linearity, High, power, dens, 7161194.html, Patent, pto, 7161194

Title: High power density and/or linearity transistors

Abstract: Field effect transistors having a power density of greater than 25 W/mm when operated at a frequency of at least 4 GHz are provided. The power density may be at least 30 W/mm when operated at 4 GHz. The power density of at least 30 W/mm may be provided at a drain voltage of 120 V. Transistors with a power density of at least 30 W/mm when operated at 8 GHz are also provided. The power density of at least 30 W/mm may be provided at a drain voltage of 120 V. Field effect transistors having a power density of greater than 20 W/mm when operated at a frequency of at least 10 GHz are also provided. Field effect transistors having a power density of at least 2.5 W/mm and a two tone linearity of at least -30 dBc of third order intermodulation distortion at a center frequency of at least 4 GHz and a power added efficiency (PAE) of at least 40% are also provided.

Patent Number: 7,161,194 Issued on 01/09/2007 to Parikh, et al.

Inventors: Parikh; Primit (Goleta, CA), Wu; Yifeng (Goleta, CA), Saxler; Adam William (Durham, NC)
Assignee: Cree, Inc. (Durham, NC)

Appl. No.: 11/005,107

Filed: December 6, 2004

Current U.S. Class: 257/194 ; 257/488

Current International Class: H01L 31/00 (20060101)

Field of Search: 257/192,194,280,488

References Cited [Referenced By]

U.S. Patent Documents


4424525	January 1984	Mimura
4471366	September 1984	Delagebeaudeuf et al.
4727403	February 1988	Hilda et al.
4755867	July 1988	Cheng
4788156	November 1988	Stoneham et al.
4946547	August 1990	Palmour et al.
5053348	October 1991	Mishra et al.
5172197	December 1992	Nguyen et al.
5192987	March 1993	Khan et al.
5200022	April 1993	Kong et al.
5210051	May 1993	Carter, Jr.
5296395	March 1994	Khan et al.
5298445	March 1994	Asano
RE34861	February 1995	Davis et al.
5389571	February 1995	Takeuchi et al.
5393993	February 1995	Edmond et al.
5523589	June 1996	Edmond et al.
5534462	July 1996	Fiordalice et al.
5592501	January 1997	Edmond et al.
5686737	November 1997	Allen
5700714	December 1997	Ogilhara et al.
5701019	December 1997	Matsumoto et al.
5705827	January 1998	Baba et al.
5804482	September 1998	Konstantinov et al.
5885860	March 1999	Weitzel et al.
5946547	August 1999	Kim et al.
5990531	November 1999	Taskar et al.
6028328	February 2000	Riechert et al.
6046464	April 2000	Schetzina
6051849	April 2000	Davis et al.
6064082	May 2000	Kawai et al.
6086673	July 2000	Molnar
6150680	November 2000	Eastman et al.
6177685	January 2001	Teraguchi et al.
6177688	January 2001	Linthicum et al.
6218680	April 2001	Carter, Jr. et al.
6255198	July 2001	Linthicum et al.
6261929	July 2001	Gehrke et al.
6316793	November 2001	Sheppard et al.
6376339	April 2002	Linthicum et al.
6380108	April 2002	Linthicum et al.
6429467	August 2002	Ando
6448648	September 2002	Boos
6462355	October 2002	Linthicum et al.
6486042	November 2002	Gehrke et al.
6489221	December 2002	Gehrke et al.
6492669	December 2002	Nakayama et al.
6515316	February 2003	Wojtowicz et al.
6521514	February 2003	Gehrke et al.
6545300	April 2003	Gehrke et al.
6548333	April 2003	Smith
6570192	May 2003	Davis et al.
6582906	June 2003	Cao et al.
6582986	June 2003	Kong et al.
6586778	July 2003	Linthicum et al.
6586781	July 2003	Wu et al.
6602763	August 2003	Davis et al.
6602764	August 2003	Linthicum et al.
6608327	August 2003	Davis et al.
6621148	September 2003	Linthicum et al.
6639255	October 2003	Inoue et al.
6686261	February 2004	Gehrke et al.
6706114	March 2004	Mueller
2001/0015446	August 2001	Inoue et al.
2001/0020700	September 2001	Inoue et al.
2001/0023964	September 2001	Wu et al.
2001/0040246	November 2001	Ishii
2002/0008241	January 2002	Edmond et al.
2002/0017696	February 2002	Nakayama et al.
2002/0066908	June 2002	Smith
2002/0079508	June 2002	Yoshida
2002/0119610	August 2002	Nishii et al.
2002/0167023	November 2002	Charvarkar et al.
2003/0017683	January 2003	Emrick et al.
2003/0020092	January 2003	Parikh et al.
2003/0102482	June 2003	Saxler
2003/0123829	July 2003	Taylor
2003/0145784	August 2003	Thompson et al.
2003/0157776	August 2003	Smith
2003/0213975	November 2003	Hirose et al.
2004/0004223	January 2004	Nagahama et al.
2004/0012015	January 2004	Saxler
2004/0021152	February 2004	Nguyen et al.
2004/0029330	February 2004	Hussain et al.
2004/0061129	April 2004	Saxler et al.
2004/0241970	December 2004	Ring
2006/0118809	June 2006	Parikh et al.

Foreign Patent Documents


0 334 006	Sep., 1989	EP
0 563 847	Oct., 1993	EP
10-050982	Feb., 1998	JP
11261053	Sep., 1999	JP
2001230407	Aug., 2001	JP
2002016087	Jan., 2002	JP
2004-342810	Dec., 2004	JP
WO 93/23877	Nov., 1993	WO
WO 01/57929	Aug., 2001	WO
WO 03/049193	Jun., 2003	WO
WO 04/008495	Jan., 2004	WO
WO 05/024909	Mar., 2005	WO

Other References

Ambacher et al., "Two Dimensional Electron Gases Induced by Spontaneous and Piezoelectric Polarization Charges in N- and Ga-face AlGaN/GaN Heterostructures," Journal of Applied Physics. vol. 85, No. 6, pp. 3222-3233 (Mar. 1999). cited by other .
Ando et al., "10-W/mm AlGaN-GaN HFET With a Field Modulating Plate," IEEE Electron Device Letters, 24(5), pp. 289-291 (May 2003). cited by other .
Asbeck et al. "Piezoelectric charge densities in AlGaN/GaN HFETs," Electronics Letters. vol. 33, No. 14, pp. 1230-1231, Jul. 1997. cited by other .
Beaumont, B. et al., "Epitaxial Lateral Overgrowth of GaN," Phys. Stat. Sol. (b) 227, No. 1, pp. 1-43 (2001). cited by other .
Ben-Yaacov et al., "AlGaN/GaN Current Aperture Vertical Electron Transistors with Regrown Channels," Journal of Applied Physics. vol. 95, No. 4, pp. 2073-2078, Feb. 2004. cited by other .
Breitschadel et al. "Minimization of Leakage Current of Recessed Gate AlGaN/GaN HEMTs by Optimizing the Dry-Etching Process," Journal of Electronic Materials. vol. 28, No. 12, pp. 1420-1423 (1999). cited by oth- er .
Burm et al. "Recessed Gate GaN MODFETS," Solid-State Electronics. vol. 41, No. 2, pp. 247-250 (1997). cited by other .
Burm et al. "Ultra-Low Resistive Ohmic Contacts on n-GaN Using Si Implantation," Applied Physics Letters. vol. 70, No. 4, 464-66, Jan. 1997. cited by other .
Chang et al., "AlGaN/GaN Modulation-Doped Field-Effect Transistors with an Mg-doped Carrier Confinement Layer," Jpn. J. Appl. Phys., 42:3316-3319, Jun. 2003. cited by other .
Chen et al. "CI2 reactive ion etching for gate recessing of AlGaN/GaN field-effect transistors," J. Vac. Sci. Technol. B. vol. 17, No. 6, pp. 2755-2758, Nov. 1999. cited by other .
Chini et al., "Power and Linearity Characteristics of Field-Plagted Recessed-Gate AlGaN-GaN HEMTs," IEEE Electron Device Letters, 25(5), pp. 229-231 (May 2004). cited by other .
Cho et al., "A New GaAs Field Effect Transistor (FET) with Dipole Barrier (DIB)," Jpn. J. Appl. Phys. 33:775-778, Jan. 1994. cited by other .
Coffie et al., Unpassivated p-GaN/AlGaN/GaN HEMTs with 7.1 W/MMF at 10 GHz, Electronic Letters online No. 20030872, 39(19), (Sep. 18, 2003). cit- ed by other .
Eastman et al. "GaN materials for high power microwave amplifiers," Mat. Res. Soc. Symp. Proc. vol. 512 (1998). cited by other .
Eastman et al. "Undoped AlGaN/GaN HEMTs for Microwave Power Amplification," IEEE Transactions on Electron Devices. vol. 48, No. 3, pp. 479-485 (Mar. 2001). cited by other .
Egawa et al. "Recessed gate ALGaN/GaN MODFET on Sapphire Grown by MOCVD," Applied Physics Letters. vol. 76, No. 1, pp. 121-123 (Jan. 2000). cited by other .
Gaska et al. "Electron Transport in AlGaN/GaN Heterostructures Grown on 6H-SiC Substrates," Applied Physics Letters. vol. 72, No. 6, pp. 707-709 (Feb. 1998). cited by other .
Gaska et al. "High-Temperature Performance of AlGaN/GaN HFET's on SiC Substrates," IEEE Electron Device Letters. vol. 18, No. 1, pp. 492-494 (Oct. 1997). cited by other .
Gaska et al., "Self-Heating in High-Power AlGaN/GaN HFET's," IEEE Electron Device Letters, 19(3), pp. 89-91 (Mar. 1998). cited by other .
Gelmont et al. "Monte Carlo simulation of electron transport in gallium nitride," Journal of Applied Physics. vol. 74, No. 3, pp. 1818-1821 (Aug. 1993). cited by other .
Heikman et al., "Growth of Fe-Doped Semi-insulating GaN by Metalorganic Chemical Vapor Deposition," Applied Physics Letters. vol. 83, No. 1, pp. 439-441 (Jul. 2002). cited by other .
Heikman, et al., "Mass Transport Regrowth of GaN for Ohmic Contacts to AlGaN/GaN," Applied Physics Letters. vol. 78, No. 19, pp. 2876, May 2001. cited by other .
Heikman et al. "Polarization Effects in AlGaN/GaN and GaN/AlGaN/GaN heterostructures," Journal of Applied Physics. vol. 93, No. 12, pp. 10114-10118 (Jun. 2003). cited by other .
Heikman, Sten J., MOCVD Growth Technologies for Applications in AlGaN/Gan High Electron Mobility Transistors, Dissertation, University of California--Santa Barbara, Sep. 2002, 190 pages. cited by other .
Hikita et al., "350V/150A AlGaN/GaN Power HFET on Silicon Substrate With Source-via Grouding (SVG) Structure," Electron Devices Meeting, 2004, pp. 803-806, IEDM Technical Digest. IEEE International (Dec. 2004). cited by other .
Kanaev et al., "Femtosecond and Ultraviolet Laser Irradiation of Graphitelike Hexagonal Boron Nitride," Journal of Applied Physics, 96(8), pp. 4483-4489 (Oct. 15, 2004). cited by other .
Kanamura et al., "A 100-W High-Gain AlGaN/GaN HEMT Power Amplifier on a Conductive N-SiC Substrate for Wireless Base Station Applications," Electron Devices Meeting, 2004, pp. 799-802, IEDM Technical Digest. IEEE International (Dec. 2004). cited by other .
Karmalkar et al. "Enhancement of Breakdown Voltage in AlGaN/GaN High Electron Mobility Transistors Using a Field Plate," IEEETransactions on Electron Devices. vol. 48, No. 8, pp. 1515-1521 (Aug. 2001). cited by oth- er .
Karmalkar et al. "RESURF AlGaN/GaN HEMT for High Voltage Power Switching," IEEE Electron Device Letters. vol. 22, No. 8, pp. 373-375 (Aug. 2001). cited by other .
Karmalkar et al., "Very High Voltage AlGaN/GaN High Electron Mobility Transistors Using a Field Plate Deposited on a Stepped Insulator," Solid State Electronics, vol. 45, pp. 1645-1652 (2001). cited by other .
Kasahara et al., "Ka-ban 2.3W Power AlGaN/GaN Heterojunction FET," IEDM Technical Digest, pp. 677-680, Dec. 2002. cited by other .
Khan et al., "High Electron Mobility Transistor Based on a GaN-AlxGa1.sub.--xN Heterojunction," Applied Physics Letters, vol. 63, No. 9, pp. 1214-1215 (Aug. 20, 1993). cited by other .
Komiak et al., "Fully Monolithic 4 Watt High Efficiency Ka-band Power Amplifier," IEEE MTT-S International Microwave Symposium Digest, vol. 3, pp. 947-950 (1999). cited by other .
Kusters et al., "Double-Heterojunction Lattice-Matched and Pseudomorphic InGaAs HEMT with -Doped InP Supply Layers and p-InP Barier Enhancement Layer Grown by LP-MOVPE," IEEE Electron Device Letters, 14(1), (Jan. 1993). cited by other .
Kuzmik et al. "Annealing of Schottky contacts deposited on dry etched AlGaN/GaN," Semiconductor Science and Technology. vol. 17, No. 11 (Nov. 2002). cited by other .
Manfra et al., "Electron Mobility Exceeding 160 000 cm.sup.2/V s in AlGaN/GaN Heterostructures Grown by Molecular-beam Epitaxy," Applied Physics Letters, 85(22), pp. 5394-5396 (Nov. 29, 2004). cited by other .
Manfra et al., "High Mobility AlGaN/GaN Heterostructures Grown by Plasma-assisted Molecular beam epitaxy on Semi-Insulating GaN Templates Prepared by Hydride Vapor Phase Epitaxy," Journal of Applied Physics, 92(1), pp. 338-345 (Jul. 1, 2002). cited by other .
Manfra et al., "High-Mobility AlGaN/GaN Heterostructures Grown by Molecular-beam Epitaxy on GaN Templates Prepared by Hydride Vapor Phase Epitaxy," Applied Physics Letters, 77(18), pp. 2888-2890 (Oct. 30, 2000). cited by other .
Neuburger et al. "Design of GaN-based Field Effect Transistor Structures based on Doping Screening of Polarization Fields," WA 1.5, 7.sup.th Wide-Gandgap III-Nitride Workshop (Mar. 2002). cited by other .
Ping et al. "DC and Microwave Performance of High-Current AlGaN/GaN Heterostructure Field Effect Transistors Grown on p-Type SiC Substrates," IEEE Electron Device Letters. vol. 19, No. 2, pp. 54-56 (Feb. 1998). cite- d by other .
Saxler et al., "III-Nitride Heterostructures on High-Purity Semi-Insulating 4H-SiC Substrates for High-Power RF Transistors," International Workshop on Nitride Semiconductors (Jul. 19, 2004). cited by other .
Sheppard et al. "High Power Demonstration at 10 GHz with GaN/AlGaN HEMT Hybrid Amplifiers." Presented at the 58.sup.th DRC, Denver, CO, Jun. 2000. cited by other .
Sheppard et al. "Improved 10-GHz Operation of GaN/AlGaN HEMTs on Silicon Carbide," Materials Science Forum. vols. 338-342, pp. 1643-1646, (2000). cited by other .
Shen et al., "High-Power Polarization-Engineered GaN/AlGaN/GaN HEMTs Without Surface Passivation," IEEE Electronics Device Letters. vol. 25, No. 1, pp. 7-9, Jan. 2004. cited by other .
Shiojima et al., "Improved Carrier Confinement by a Buried p-Layer in the AlGaN/GaN HEMT Structure," IEICE Trans. Electron., E83-C(12), (Dec. 2000). cited by other .
Sriram et al. "RF Performance of AlGaN/GaN MODFET's on High Resistivity SiC Substrates," Presentation at Materials Research Society Fall Symposium, 1997. cited by other .
Sriram et al. "SiC and GaN Wide Bandgap Microwave Power Transistors," IEEE Samoff Symposium, Pittsburgh, PA, Mar. 18, 1998. cited by other .
Sullivan et al. "High-Power 10-GHz Operation of AlGaN HFET's on Insulating SiC," IEEE Electron Device Letters. vol. 19, No. 6, pp. 198-200 (Jun. 1998). cited by other .
"Thick AIN template on SiC substrate--Novel semi insulating substrate for GaN-based devices," .COPYRGT. 2003 by TDI, Inc., http://www.tdii.com/products/AIN.sub.--SiCT.html. cited by other .
Tilak et al., "Influence of Barrier Thickness on the High-Power Performance of AlGaN/Gan HEMTs," IEEE Electron Device Letters, 22(11), pp. 504-506 (Nov. 2001). cited by other .
"Improved Dielectric Passivation for Semiconductor Devices," U.S. Appl. No. 10/851,507, filed May 22, 2004. cited by other .
"Wide Bandgap Transistor Devices With Field Plate," U.S. Appl. No. 10/930,160, filed Aug. 31, 2004. cited by other .
"Cascode Amplifier Structures Including Wide Bandgap Field Effect Transistor With Field Plate," U.S. Appl. No. 10/856,098, filed May 28, 2004. cited by other .
"Nitride-Based Transistors and Methods of Fabrication Thereof Using Non-Etched Contact Recesses," U.S. Appl. No. 10/617,843, filed Jul. 11, 2003. cited by other .
"Nitride-Based Transistors with a Protective Layer and a Low-Damage Recess and Methods of Fabrication Thereof," U.S. Appl. No. 10/758,871, filed Jan. 16, 2004. cited by other .
"Co-Doping for Fermi Level Control in Semi-Insulating Group III Nitrides," U.S. Appl. No. 10/752,970, filed Jan. 7, 2004. cited by other .
"Cap Layers and/or Passivation Layers for Nitride-Based Transistors, Transistor Structures and Methods of Fabricating the Same," U.S. Appl. No. 10/996,249, filed Nov. 23, 2004. cited by other .
"Methods of Having Laterally Grown Active Region and Methods of Fabricating Same," U.S. Appl. No. 10/899,215, filed Jul. 26, 2004. cited by other .
"Silicon Carbide on Diamond Substrates and Related Devices and Methods," U.S. Appl. No. 10/707,898, filed Jan. 22, 2004. cited by other .
"Nitride Heterojunction Transistors Having Charge-Transfer Induced Energy Barriers and Methods of Fabricating the Same," U.S. Appl. No. 10/772,882, filed Feb. 5, 2004. cited by other .
"Methods of Fabricating Nitride-Based Transistors with a Cap Layer and a Recessed Gate," U.S. Appl. No. 10/897,726, filed Jul. 23, 2004. cited by other .
"Semiconductor Devices Having a Hybrid Channel Layer Current Aperture Transistors and Methods of Fabricating Same" U.S. Appl. No. 10/849,589, filed May 20, 2004. cited by other .
"Methods of Fabricating Nitride-Based Transistors Having Regrown Ohmic Contact Regions and Nitride-Based Transistors Having Regrown Ohmic Contact Regions," U.S. Appl. No. 10/849,617, filed May 20, 2004. cited by other .
"Field Effect Transistors (FETS) Having Multi-Watt Output Power at Millimeter-Wave Frequencies," U.S. Appl. No. 11/005,423, filed Dec. 6, 2004. cited by other .
"Group III Nitride Field Effect Transistors (FETs) Capable of Withstanding High Temperature Reverse Bias Test Conditions," U.S. Appl. No. 11/080,905, filed Mar. 15, 2005. cited by other .
"Aluminum Free Group III-Nitride Based High Electron Mobility Transistors and Methods of Fabricating Same," U.S. Appl. No. 11/118,575, filed Apr. 29, 2005. cited by other .
"Binary Group III-Nitride Based High Electron Mobility Transistors and Methods of Fabricating Same," U.S. Appl. No. 11/118,675, filed Apr. 29, 2005. cited by other .
"Composite Substrates of Conductive And Insulating or Semi-Insulating Group III-Nitrides For Group III-Nitride Devices," U.S. Appl. No. 11/103,127, filed Apr. 11, 2005. cited by other .
"Thick Semi-Insulating or Insulating Epitaxial Gallium Nitride Layers and Devices Incorporating Same," U.S. Appl. No. 11/103,117, filed Apr. 11, 2005. cited by other .
Walker, J. L. B. (Ed.), High Power GaAs FET Amplifiers, Norwood, MA: Artech House, pp. 119-120 (1993). cited by other .
Wu et al., "3.5-Watt AlGaN/GaN HEMTs and Amplifiers at 35 GHz," IEDM-2003, Cree, Inc, Dec. 2003. cited by other .
Wu et al., "30-W/mm GaN HEMTs by Field Plate Optimization," IEEE Electron Device Letters, 25(3), pp. 117-119 (Mar. 2004). cited by other .
Wu et al., "Bias-dependent Performance of High-Power AlGaN/GaN HEMTs," IEDM Technical Digest, p. 378-380 (2001). cited by other .
Wu et al. "High Al-Content AlGaN/GaN MODFET's for Ultrahigh Performance," IEEE Electron Device Letters. vol. 19, No. 2, pp. 50-53 (Feb. 1998). cite- d by other .
Wu et al., "Measured Microwave Power Performance of AlGaN/GaN MODFET," IEEE Electron Device Letters, vol. 17, No. 9, pp. 455-457 (Sep. 9, 1996). cited by other .
Yu et al., "Schottky Barrier Engineering in III-V Nitrides via the Piezoelectric Effect," Applied Physics Letters, 73(13), pp. 1880-1882 (Sep. 28, 1998). cited by other .
Zhang et al., "High Breakdown GaN HEMT with Overlapping Gate Structure," IEEE Electron Device Letters, 21(9), pp. 421-423 (Sep. 2000). cited by other .
Parikh et al., "Development of Gallium Nitride Epitaxy and Associated Material-Device Correlation for RF, Microwave 5nd MM-wave Applications," Cree, Inc. (35 slides). May 2004. cited by other .
Wu et al., "3.5-Watt AlGaN/GaN HEMTs and Amplifiers at 35 GHz," Electron Devices Meeting, 2003. IEDM '03 Technical Digest. IEEE International. Dec. 8-10, 2003. cited by other .
Wu et al., "Linearity Performance of GaN HEMTs With Field Plates," Device Research Conference, 2004. 62nd DRC. Conference Digest. Jun. 21-23, 2004. cited by other .
Wu et al., "Linearity Performance of GaN HEMTs With Field Plates," Device Research Conference, 2004. 62nd DRC. Jun. 21-23, 2004. cited by other.

Primary Examiner: Prenty; Mark V.
Attorney, Agent or Firm: Myers Bigel Sibley & Sajovec

Claims

That which is claimed is:

1. A field effect transistor having a power density of greater than 25 W/mm when operated at a frequency of at least 4 GHz.

2. The field effect transistor of claim 1, wherein the power density is provided at a compression of not greater than 3 dB.

3. The field effect transistor of claim 1, wherein the power density is at least 30 W/mm when operated at 4 GHz.

4. The field effect transistor of claim 3, wherein the power density of at least 30 W/mm is provided at a drain voltage of 120 V.

5. The field effect transistor of claim 1, wherein the power density is at least 30 W/mm when operated at 8 GHz.

6. The field effect transistor of claim 5, wherein the power density of at least 30 W/mm is provided at a drain voltage of 120 V.

7. The field effect transistor of claim 1, wherein the transistor comprises a high electron mobility transistor (HEMT).

8. The field effect transistor of claim 7, wherein the transistor comprises a Group III-nitride HEMT.

9. The field effect transistor of claim 8, wherein the Group III-nitride HEMT comprises: a GaN channel layer; an AlN layer on the GaN channel layer; an AlGaN layer on the AlN layer; a gate contact on the AlGaN layer; source and drain contacts on the AlGaN layer; an insulating layer on the gate contact; and a field plate on the insulating layer and electrically coupled to the gate contact.

10. The field effect transistor of claim 9, wherein the field plate has a field plate length (L.sub.F) of from about 0.3 .mu.m to about 1.1 .mu.m.

11. The field effect transistor of claim 10, wherein the field plate length is from 0.3 0.5 .mu.m.

12. The field effect transistor of claim 10, wherein the field plate length is from 0.9 1.1 .mu.m.

13. A field effect transistor having a power density of greater than 20 W/mm when operated at a frequency of at least 10 GHz.

14. The field effect transistor of claim 13, wherein the power density is provided at a compression of not greater than 3 dB.

15. The field effect transistor of claim 13, wherein the power density of greater than 20 W/mm is provided at a drain voltage of 70 V.

16. The field effect transistor of claim 15, wherein the transistor comprises a high electron mobility transistor (HEMT).

17. The field effect transistor of claim 16, wherein the transistor comprises a Group III-nitride HEMT.

18. The field effect transistor of claim 17, wherein the Group III-nitride HEMT comprises: a GaN channel layer; an AlN layer on the GaN channel layer; an AlGaN layer on the AlN layer; a gate contact on the AlGaN layer; source and drain contacts on the AlGaN layer; an insulating layer on the gate contact; and a field plate on the insulating layer and electrically coupled to the gate contact.

19. The field effect transistor of claim 18, wherein the field plate has a field plate length (L.sub.F) of from about 0.3 .mu.m to about 1.1 .mu.m.

20. The field effect transistor of claim 19, wherein the field plate length is from 0.3 0.5 .mu.m.

21. The field effect transistor of claim 19, wherein the field plate length is from 0.9 1.1 .mu.m.

22. A field effect transistor having a power density of at least 2.5 W/mm and a two tone linearity of at least -30 dBc of third order intermodulation distortion (IM3) at a center frequency of at least 4 GHz and a power added efficiency (PAE) of at least 40% with IM3 of at least -30 dBc.

23. The field effect transistor of claim 22, wherein the power density is provided at a compression of not greater than 3 dB.

24. The field effect transistor of claim 22, wherein the drain voltage power density is provided at a drain voltage of 48 V.

25. The field effect transistor of claim 22, wherein the PAE is at least 50%.

26. The field effect transistor of claim 22, wherein the power density is at least 5 W/mm with IM3 of at least -30 dBc.

27. The field effect transistor of claim 22, wherein the power density is provided at a drain voltage of 108 V.

28. The field effect transistor of claim 22, wherein the power density is at least 10 W/mm with IM3 of at least -30 dBc.

29. The field effect transistor of claim 28, wherein the power density is provided at a drain voltage of 108 V.

30. The field effect transistor of claim 22, wherein the transistor comprises a high electron mobility transistor (HEMT).

31. The field effect transistor of claim 30, wherein the transistor comprises a Group III-nitride HEMT.

32. The field effect transistor of claim 31, wherein the Group III-nitride HEMT comprises: a GaN channel layer; an AlN layer on the GaN channel layer; an AlGaN layer on the AlN layer; a gate contact on the AlGaN layer; and source and drain contacts on the AlGaN layer.

33. The field effect transistor of claim 32, further comprising: an insulating layer on the gate contact; and a field plate on the insulating layer and electrically coupled to the gate contact.

34. The field effect transistor of claim 33, wherein the field plate has a field plate length (L.sub.F) of from about 0.3 .mu.m to about 1.1 .mu.m.

35. The field effect transistor of claim 34, wherein the field plate length is about 0.7 .mu.m.

Description

FIELD OF THE INVENTION

The present invention relates to semiconductor devices and, more particularly, to transistors.

BACKGROUND

Materials such as silicon (Si) and gallium arsenide (GaAs) have found wide application in semiconductor devices. These, more familiar, semiconductor materials may not be well suited for higher power and/or high frequency applications, however, because of their relatively small bandgaps (e.g., 1.12 eV for Si and 1.42 for GaAs at room temperature) and/or relatively small breakdown voltages.

In light of the difficulties presented by Si and GaAs, interest in high power, high temperature and/or high frequency applications and devices has turned to wide bandgap semiconductor materials such as silicon carbide (2.996 eV for alpha SiC at room temperature) and the Group III nitrides (e.g., 3.36 eV for GaN at room temperature). These materials, typically, have higher electric field breakdown strengths and higher electron saturation velocities as compared to gallium arsenide and silicon.

A device of particular interest for high power and/or high frequency applications is the High Electron Mobility Transistor (HEMT), which, in certain cases, is also known as a modulation doped field effect transistor (MODFET). These devices may offer operational advantages under a number of circumstances because a two-dimensional electron gas (2DEG) is formed at the heterojunction of two semiconductor materials with different bandgap energies, and where the smaller bandgap material has a higher electron affinity. The 2DEG is an accumulation layer in the undoped ("unintentionally doped"), smaller bandgap material and can contain a very high sheet electron concentration in excess of, for example, 10.sup.13 carriers/cm.sup.2. Additionally, electrons that originate in the wider-bandgap semiconductor transfer to the 2DEG, allowing a high electron mobility due to reduced ionized impurity scattering.

This combination of high carrier concentration and high carrier mobility can give the HEMT a very large transconductance and may provide a strong performance advantage over metal-semiconductor field effect transistors (MESFETs) for high-frequency applications.

High electron mobility transistors fabricated in the gallium nitride/aluminum gallium nitride (GaN/AlGaN) material system have the potential to generate large amounts of RF power because of the combination of material characteristics that includes the aforementioned high breakdown fields, their wide bandgaps, large conduction band offset, and/or high saturated electron drift velocity. A major portion of the electrons in the 2DEG is attributed to polarization in the AlGaN. HEMTs in the GaN/AlGaN system have already been demonstrated. U.S. Pat. Nos. 5,192,987 and 5,296,395 describe AlGaN/GaN HEMT structures and methods of manufacture. U.S. Pat. No. 6,316,793, to Sheppard et al., which is commonly assigned and is incorporated herein by reference, describes a HEMT device having a semi-insulating silicon carbide substrate, an aluminum nitride buffer layer on the substrate, an insulating gallium nitride layer on the buffer layer, an aluminum gallium nitride barrier layer on the gallium nitride layer, and a passivation layer on the aluminum gallium nitride active structure.

Wide bandgap GaN-based high-electron-mobility-transistors (HEMTs) have come a long way as microwave devices since their description in 1993 in Khan et al., Appl. Phys. Lett., vol. 63, p. 1214, 1993, and a demonstration of their power capability in 1996 in Wu et al., IEEE Electron Device Lett., vol. 17, pp. 455 457, September, 1996. Many research groups have presented devices with power densities exceeding 10 W/mm, a ten-fold improvement over conventional III V devices. See Tilak et al., IEEE Electron Device Lett., vol. 22, pp. 504 506, November, 2001; Wu et al., IEDM Tech Dig., Dec. 2 5, 2001, pp. 378 380; and Ando et al., IEEE Electron Device Lett., vol. 24, pp. 289 291, May, 2003. Much of the previous work covered material quality, choice of substrate, epi-layer structures and processing techniques. Less effort has been put on advanced device designs, leaving room for further improvement. An overlapping gate structure, or field plate, was used by Zhang et al. with GaN HEMTs for high-voltage switching applications. Zhang et al., IEEE Electron Device Lett., vol. 21, pp. 421 423, September, 2000. Following this, Karmalkar et al. performed simulations for the field plate structure, predicting up to five times enhancement in breakdown voltages. Karmalkar et al., IEEE Trans. Electron Devices, vol. 48, pp. 1515 1521, August, 2001. However, fabricated devices at that time had low cutoff frequencies, not suitable for microwave operation. Ando et al. recently used a similar structure with smaller gate dimensions and demonstrated performance of 10.3 W output power at 2 GHz using a 1-mm-wide device on a SiC substrate. Ando et al., IEEE Electron Device Lett., vol. 24, pp. 289 291, May, 2003. Chini et al. implemented a new variation of the field-plate design with further reduced gate dimensions and obtained 12 W/mm at 4 GHz from a 150-.mu.m-wide device on a sapphire substrate. Chini et al., IEEE Electron Device Lett., vol. 25, No. 5, pp. 229 231, May, 2004.

Modern communication applications also may require high linearity for power devices. Chini et. al. reported two-tone linear power of 2.4 W/mm with PAE of 53% at 4 GHz from FP devices at a 3.sup.rd-order-intermodulation level (IM.sub.3) of -30 dBc. Chini et al., IEEE Electron Device Lett., vol. 25, No. 5, pp. 229 231, May, 2004.

SUMMARY OF THE INVENTION

Some embodiments of the present invention provide field effect transistors having a power density of greater than 25 W/mm when operated at a frequency of at least 4 GHz. In some embodiments, the power density is at least 30 W/mm when operated at 4 GHz. Furthermore, the power density of at least 30 W/mm may be provided at a drain voltage of 120 V. In some embodiments, the power density is provided at a compression of not greater than 3 dB.

In still further embodiments of the present invention, the power density is at least 30 W/mm when operated at 8 GHz. The power density of at least 30 W/mm may be provided at a drain voltage of 120 V.

In particular embodiments of the present invention, the transistors are a high electron mobility transistor (HEMT). The transistors may be Group III-nitride HEMTs. The Group III-nitride HEMTs may include a GaN channel layer, an AlN layer on the GaN channel layer, an AlGaN layer on the AlN layer, a gate contact on the AlGaN layer, source and drain contacts on the AlGaN layer, an insulating layer on the gate contact and a field plate on the insulating layer that is electrically coupled to the gate contact. The field plate may have a field plate length (L.sub.F) of from about 0.3 .mu.m to about 1.1 .mu.m. In particular embodiments, the field plate length is from 0.3 0.5 .mu.m. In other embodiments, the field plate length is from 0.9 1.1 .mu.m.

In some embodiments, field effect transistors having a power density of greater than 20 W/mm when operated at a frequency of at least 10 GHz is provided. The power density of greater than 20 W/mm may be provided at a drain voltage of 70 V. In some embodiments, the power density is provided at a compression of not greater than 3 dB. The transistors may be high electron mobility transistors (HEMTs). The transistors may be Group III-nitride HEMTs. The Group III-nitride HEMTs may include a GaN channel layer, an AlN layer on the GaN channel layer, an AlGaN layer on the AlN layer, a gate contact on the AlGaN layer, source and drain contacts on the AlGaN layer, an insulating layer on the gate contact and a field plate on the insulating layer that is electrically coupled to the gate contact. The field plate may have a field plate length (L.sub.F) of from about 0.3 .mu.m to about 1.1 .mu.m. In some embodiments, the field plate length is from 0.3 0.5 .mu.m. In other embodiments, the field plate length is from 0.9 1.1 .mu.m.

Still further embodiments of the present invention provide field effect transistors having a power density of at least 2.5 W/mm and a two tone linearity of at least -30 dBc of third order intermodulation distortion (IM3) at a center frequency of at least 4 GHz and a power added efficiency (PAE) of at least 40%. The power density may be provided at a drain voltage of 48 V. The PAE may be at least 50%. The power density may be at least 5 W/mm, while maintaining IM3 of at least -30 dBc. The power density may be provided at a drain voltage of 108 V. In some embodiments, the linear power density is at least 10 W/mm, while maintaining IM3 of at least -30 dBc. In such a case, the power density may be provided at a drain voltage of 108 V. In some embodiments, the power density is provided at a compression of not greater than 3 dB.

In particular embodiments of the present invention, the transistors are high electron mobility transistors (HEMTs). The transistors may be Group III-nitride HEMTs. In particular embodiments, the Group III-nitride HEMTs include a GaN channel layer, an AlN layer on the GaN channel layer, an AlGaN layer on the AlN layer, a gate contact on the AlGaN layer and source and drain contacts on the AlGaN layer. The HEMT may also include an insulating layer on the gate contact and a field plate on the insulating layer that is electrically coupled to the gate contact. The field plate may have a field plate length (L.sub.F) of from about 0.3 .mu.m to about 1.1 .mu.m. In particular embodiments, the field plate length is about 0.7 .mu.m.

Transistors having various combinations and/or sub-combinations of transistor characteristics described above may also be provided according to some embodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional diagram of a transistor according to some embodiments of the present invention.

FIG. 2 is a graph of current-gain and power-gain cutoff frequencies, f.sub.t and f.sub.MAX, as a function of field plate dimension L.sub.F. The devices were biased at V.sub.DS=10 V and I.sub.D=300 mA/mm, where the best f.sub.t is typically located. Gate length and width were 0.55 .mu.m and 2.times.123 .mu.m with L.sub.GS=1 .mu.m and L.sub.FD>2 .mu.m.

FIG. 3 is a graph of power performance versus length of field plate L.sub.F when measured at 4 GHz with drain biases of 28 and 48 V for the devices of FIG. 2.

FIG. 4 is a graph of power performance and large signal gain versus length of field plate L.sub.F when measured at 8 GHz with drain bias of 48 V for the devices of FIG. 2.

FIG. 5 is a power sweep graph at 4 GHz for 246-.mu.m-wide devices showing 32.2 W/mm power density and 54.8% power added efficiency (PAE) when biased at 120 V. Linear gain is 16.9 dB and associated large-signal gain is 14 dB. Device dimensions: L.sub.GS=1 .mu.m, L.sub.G=0.55 .mu.m; L.sub.F=1.1 .mu.m, and L.sub.FD=3 .mu.m.

FIG. 6 is a power sweep graph at 8 GHz for 246-.mu.m-wide devices showing 30.6 W/mm power density and 49.6% PAE when biased at 120 V. Linear gain is 10.7 dB (-2.3 dB compression). Device dimensions: L.sub.GS=1 .mu.m, L.sub.G=0.55 .mu.m; L.sub.F=0.9 .mu.m, and L.sub.FD=3 .mu.m.

FIG. 7 is a graph of linearity performance of a device with L.sub.F=0.7 .mu.m at V.sub.DS=48V and I.sub.Q=20 mA/mm, which achieved a 57% PAE at -30 dBc IM.sub.3 with associated power of 3.7 W/mm. The device dimensions were 0.5.times.246 .mu.m.sup.2 with L.sub.G=0.5 .mu.m, L.sub.GS=1 .mu.m and L.sub.FD=2 .mu.m. Single tone power at 3 dB compression was P.sub.3dB=8.8 W/mm with PAE=71%.

FIG. 8 is a graph of linearity performance of a device with L.sub.F=1.1 .mu.m at V.sub.DS=108V and I.sub.Q=20 mA/mm, which achieved a 41% PAE at -30 dBc IM.sub.3 with associated power of 10 W/mm. The device dimensions were 0.5.times.246 .mu.m.sup.2 with L.sub.G=0.5 .mu.m, L.sub.GS=1 .mu.m and L.sub.FD=3 .mu.m. Single tone power at 3 dB compression was P.sub.3dB=24 W/mm with PAE=48%.

FIGS. 9 and 10 are graphs of cutoff frequency versus bias current and voltage respectively for devices with a field plate length L.sub.F (labeled Lp in FIGS. 10 and 11) ranging from 0 to 1.1 .mu.m, L.sub.G=0.5 .mu.m, L.sub.GS=1 .mu.m and L.sub.FD>2 .mu.m.

FIG. 11 is a graph of current versus voltage characteristics for devices according to some embodiments of the present invention. The devices of FIG. 11 have a very-high n.mu. product: 2350.times.10.sup.13 (Vs).sup.-1, low on-resistance: 2.1 2.3 .OMEGA.-mm and I.sub.D,MAX>1200 mA/mm. For the devices of FIG. 11, L.sub.F=0.7 .mu.m, L.sub.G=0.5 .mu.m, L.sub.GS=1 .mu.m and L.sub.FD=2 .mu.m.

FIG. 12 is a graph of power performance versus L.sub.F at increasing voltages with L.sub.G=0.5 .mu.m, L.sub.GS=1 .mu.m and L.sub.FD>2 .mu.m.

FIG. 13 is a graph of linearity performance of a device without a field plate V.sub.DS=48V and I.sub.Q=20 mA/mm, which achieved a 56% PAE at -30 dBc IM.sub.3 with associated power of 3.4 W/mm. The device dimensions were 0.5.times.246 .mu.m.sup.2 with L.sub.G =0.5 .mu.m and L.sub.GS=1 .mu.m. Single tone power at 3 dB compression was P.sub.3dB=8 W/mm with PAE=70%.

FIG. 14 is a graph of performance of a device with a field plate at 10 GHz, V.sub.DS=70V and I.sub.Q=20 mA/mm, which achieved a 50% PAE with associated power density of 20 W/mm. The device dimensions were a gate width W.sub.G of 246 .mu.m, L.sub.F=0.7 .mu.m, L.sub.FD=2 .mu.m, L.sub.G=0.5 .mu.m and L.sub.GS=1 .mu.m.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. However, this invention should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the thickness of layers and regions are exaggerated for clarity. Like numbers refer to like elements th