Patent
Ultra-high-speed photoconductive devices using semi-insulating layers
| العنوان: | Ultra-high-speed photoconductive devices using semi-insulating layers |
|---|---|
| Patent Number: | 5,168,069 |
| تاريخ النشر: | December 01, 1992 |
| Appl. No: | 07/312,133 |
| Application Filed: | February 17, 1989 |
| مستخلص: | An ultra-high-speed photoconductive device is described which comprises a homoepitaxial semi-insulating III-V layer, or body, upon which ohmic/conductive contacts, or strips, separated by a small gap, are formed. The semi-insulating body, or layer, is produced by low temperature growth of III-V compounds by MBE. In a GaAs embodiment, the layer is grown under arsenic stable growth conditions, at a substrate temperature preferably in the range of 150.degree. to about 300.degree. C. |
| Inventors: | Smith, Frank W. (Cambridge, MA); Hollis, Mark A. (Concord, MA); Calawa, Arthur R. (Wellesley, MA); Diadiuk, Vicky (Lincoln, MA); Le, Han Q. (Newton, MA) |
| Assignees: | Massachusetts Institute of Technology (Cambridge, MA) |
| Claim: | We claim |
| Claim: | 1. A method of making a non-Schottky barrier type photoconductive detector comprising the steps of |
| Claim: | a) forming a semi-including homoepitaxial layer of III-V material by molecular beam deposition of a flux of Group III and Group V molecular beams species on a substrate at a substrate temperature below 400.degree. C.; |
| Claim: | b) heat treating the layer in an ambient which incorporates an excess of the more volatile of said species into said layer; and |
| Claim: | c. forming a first electrical conductor comprising an ohmic contact on said layer with a gap separating one portion of said conductor from another portion of said conductor. |
| Claim: | 2. The method of claim 1 wherein the semi-insulating layer is comprised of GaAs and the temperature is about equal to or less than 300.degree. C. and the more volatile species is As. |
| Claim: | 3. The method of claim 1 wherein the semi-insulating layer is comprised of GaAs and the temperature is in the range of 150.degree.-300.degree. C. and the more volatile species is As, and the excess is about 1%. |
| Claim: | 4. The method of claim 1 wherein the electrical conductor comprises n-type GaAs upon which a metallization film is formed. |
| Claim: | 5. The method of claim 1 in which a second conductive layer is formed between the first electrical conductor and the semi-insulating layer. |
| Claim: | 6. The method of claim 1 wherein a thin conductive layer is formed on the semi-insulating layer and another semi-insulating layer is formed on the thin conductive layer. |
| Claim: | 7. The method of claim 1 in which a thin conductive layer is formed between a planar surface of the contact and a planar surface of the semi-insulating layer. |
| Claim: | 8. A method of making a III-V photoconductive device on a structure comprising the steps of |
| Claim: | a) forming an electrically insulating homoepitaxial layer of III-V material by molecular beam deposition of a flux of III and V materials on a substrate in a chamber at a predetermined growth temperature below about 450.degree. C. and above about 50.degree. C.; |
| Claim: | b) subjecting said insulating layer to a heat treatment at an elevated temperature in an ambient containing the more volatile of sale III-V materials to incorporate an excess of the more volatile material into said layer; |
| Claim: | c) forming a stabilizing layer of III-V material over said heat treated layer to minimize out diffusion of the more volatile of said III-V materials; |
| Claim: | d) forming ohmic contacts on said stabilizing layer said contacts being separated by a gap. |
| Claim: | 9. The method of claim 8 wherein the insulating layer is formed of GaAs at a growth temperature less than about 300.degree. C. and the insulating layer has a resistivity much greater than the resistivity of the same material grown by molecular beam deposition at about 580.degree. C. or higher on the same substrate material under otherwise substantially the same growth conditions. |
| Claim: | 10. A method of making a high-speed photoconductive detector comprising the steps of |
| Claim: | a) forming a semi-insulating homoepitaxial layer of III-V material by molecular beam deposition of a flux of Group III and Group V molecular beam species on a substrate at a substrate temperature less than about 450.degree. C.; |
| Claim: | b) heat treating the layer at a temperature above 450.degree. C. in an ambient containing the more volatile of said species to achieve an excess of said more volatile species in said layer; and |
| Claim: | c) forming an electrical conductor on said layer with a gap separating one portion of said conductor from another portion of said conductor. |
| Claim: | 11. The method of claim 10 wherein the flux comprises two Group III species, one of which is Ga, and one Group V species, As, and the semi-insulating layer formed is comprised of GaAs and the other Group III element. |
| Claim: | 12. The method of claim 10 wherein the semi-insulating layer is comprised of GaAs and the substrate temperature is in the range of 150.degree.-300.degree. C. |
| Claim: | 13. The method of claim 10 wherein the electrical conductor comprises n-type GaAs upon which a metallization film is formed. |
| Claim: | 14. The method of claim 10 wherein the electrical conductor forms an ohmic contact to the semi-insulating layer. |
| Claim: | 15. A method of making a III-V photoconductive device on a structure comprising the steps of |
| Claim: | a) forming an electrically insulating homoepitaxial layer of III-V material by molecular beam deposition of a flux of III and V materials on a substrate in a chamber at a substrate temperature below about 450.degree. C.; |
| Claim: | b) subjecting said insulating layer to a heat treatment at an elevated temperature above 450.degree. C. in an ambient containing the more volatile of said III-V materials; |
| Claim: | c) forming a further layer of material over said heat treated layer to minimize out diffusion of the move volatile of said III-V materials; |
| Claim: | d) forming ohmic contacts on said further layer, said contacts being separated by a gap. |
| Claim: | 16. The method of claim 15 wherein the insulating layer is formed of material including GaAs and the insulating layer so formed has a resistivity much greater than other insulating layers of the same materials grown under the same conditions, except that the other layers are grown at temperatures above 580.degree. C. |
| Claim: | 17. The method of claim 16 wherein the resistivity is at least 10.sup.5 ohm-cm. |
| Claim: | 18. A method of making a non-Schottky barrier type photoconductive detector comprising the steps of |
| Claim: | a) forming a semi-insulating homoepitaxial layer of III-V material by molecular beam deposition of a flux of Group III and Group V molecular beams species on a substrate at a predetermined substrate temperature below 450.degree. C.; |
| Claim: | b) heat treating the homoepitaxial layer in an ambient which incorporates an excess of the more volatile of said species into said layer; and |
| Claim: | c) forming an ohmic contact on said layer with a gap separating one portion of said contact from another portion of said contact. |
| Claim: | 19. The method of claim 18 wherein the contact is comprised of n-type GaAs upon which a metallization film is formed. |
| Claim: | 20. A method of making a III-V photoconductive device on a structure comprising the steps of |
| Claim: | a) forming an electrically insulating homoepitaxial layer of III-V material by molecular beam deposition of a flux of III and V materials on a substrate in a chamber at a predetermined growth temperature in the range of about 450.degree. C. to 50.degree. C. and wherein one of said materials is more volatile than the other; |
| Claim: | b) subjecting said insulating layer to a heat treatment in an ambient containing the more volatile of said III-V materials to introduce an excess of said volatile material into said layer; |
| Claim: | c) forming a stabilizing layer over said heat treated layer to minimize out diffusion of the more volatile of said III-V materials; and |
| Claim: | d) forming ohmic contact son said stabilizing layer said contacts being separated by a gap. |
| Claim: | 21. The method of claim 20 wherein the insulating layer is formed of GaAs at a growth temperature of about 300.degree. C. or less and the insulating layer has a resistivity much greater than the resistivity of the same material grown at about 580.degree. C. or higher under otherwise the same conditions. |
| Claim: | 22. A method of making a high-speed photoconductive detector comprising the steps of |
| Claim: | b) forming an excess of a more volatile one of a said species in said layer; |
| Claim: | c) minimizing out diffusion of said excess species form said layer, and |
| Claim: | d) forming an electrical conductor on said layer with a gap separating one portion of said conductor from another portion of said conductor. |
| Current U.S. Class: | 437/5; 437/22; 437/25; 437/126; 437/133 |
| Current International Class: | H01L 3138; H01L 21265 |
| Patent References Cited: | 3530298 September 1970 Hubbard et al. 3716804 February 1973 Groschwitz 3917943 November 1975 Auston 3923380 December 1975 Kaisha et al. 3942132 March 1976 Zinn 3949224 April 1976 Klingen 3958862 May 1976 Victor 3962657 June 1976 Redman et al. 4020341 April 1977 Javan 4218618 August 1980 Mourou 4291323 September 1981 Bachmann 4293956 October 1981 Alstatt 4301362 November 1981 Mourou 4376285 March 1983 Leonberger 4396833 August 1983 Pan 4525871 June 1985 Foyt et al. 4713354 December 1987 Egawa et al. 4807006 February 1989 Rogers et al. 4839510 June 1989 Okabe et al. 4933542 June 1990 Bokon et al. 4978910 December 1990 Knox et al. |
| Other References: | "High-Speed InP Optoelectronic Switch", Leonberger et al., Appl. Phys. Lett. 35(9), Nov. 1, 1979, pp. 712-714. "GaAs Infrared Source for Optoelectronic Applications", 1963 International Solid-State Ckts Con. pp. 108,109, Baird et al. "Isolation of Junction Devices in GaAs Using Proton Bombardment", Foyt et al., Solid-State Electronics, 1969, vol. 12, pp. 209-214. "Gain and Bandwidth of Fast Near-Infrared Photodetectors: A Comparison of Diodes, Phototransistors, and Photoconductive Devices", IEEE Transactions on Electron Devices, vol. ED-29, No. 9, Sep. 1982, pp. 1420-1431, Beneking, H. "Microwave Switching Performance of High-Speed Optoelectronic Switches", IEE Proceedings-I, vol. 128, No. 6, Dec. 1981, pp. 193-196, Platte, W. "Carrier Relaxation Mechanisms in CdS.sub.0.5 Se.sub.0.5 Optoelectronic Switches", Journal of Applied Physics, vol. 51, No. 9, Sep. 1980, pp. 4889-4893, Mathur et al. "Summary Abstract: Protection of an Interrupted Molecular-Beam-Epitaxially Grown Surface by a Thin Epitaxial Layer of InAs", Chang et al., J. Vac. Sci. Technol. B3(2), Mar./Apr. 1985, pp. 518/519. "New MBE Buffer Used to Eliminate Backgating in GaAs MESFET's", Smith et al., IEEE Electron Device Letters, 9, Feb./1988, No. 2, pp. 77-80. "Proceedings of the 14th Annual Conference on the Physics and Chemistry of Semiconductor Interfaces", Journal of Applied Physics 57, Mar./1985, No. 6, pp. 1922-1927. "Effect of Arsenic Partial Pressure on Capless Anneal of Ion-Implanted GaAs", Kasahara et al., J. of the Electrochem Society, vol. 126 (1979) No. 11, pp. 1997-2001. "Low-Temperature Growth of GaAs and AlAs-GaAs Quantum-Well Layers by Modified Molecular Beam Epitaxy", Horikoshi et al., Japanese Journal of Applied Physics 25 (1986) Oct. No. 10, part 2, pp. L868-L870. |
| Primary Examiner: | Chaudhuri, Olik |
| Assistant Examiner: | Trinh, Loc Q. |
| Attorney, Agent or Firm: | Hamilton, Brook, Smith & Reynolds |
| رقم الانضمام: | edspgr.05168069 |
| قاعدة البيانات: | USPTO Patent Grants |
| الوصف غير متاح. |