W.T. Lindley

Silicon‐ and selenium‐ion‐implanted GaAs reproducibly annealed at temperatures up to 950 °C

A pyrolytic Si3N4 encapsulation technique has been used to permit reproducible annealing of implanted GaAs at temperatures as high as 950 °C. At low doses, electrical activity ≳70% has been achieved for both Si and Se. At high doses, sheet carrier concentrations and sheet resistivities of 1.8×1014/cm2 and 20 Ω/⧠, respectively, for Si and 7×1013/cm2 and 44 Ω/⧠, respectively, for Se have been measured.

EFFICIENT DOPING OF GaAs BY Se+ ION IMPLANTATION

Efficient doping of GaAs by ion implantation has been obtained using Se+ ions. For a Se+ dose of 3 × 1012/cm2 implanted at 400 keV, a peak carrier concentration of 2 × 1017/cm3 occurred at a depth of 750 A, with a standard deviation of 500 A. Integration of the excess carrier concentration caused by the implantation indicates that for this ion dose at least 50% of the implanted ions are electrically active. For larger doses the doping efficiency decreases, and the carrier concentration approaches a limiting value of approximately 1019/cm3. The lowest observed sheet resistance for the implanted layer, about 250 Ω/square, occurred for a Se+ dose of 2 × 1014/cm2.

n‐p JUNCTION PHOTODETECTORS IN InSb FABRICATED BY PROTON BOMBARDMENT

We have fabricated n‐p junction photovoltaic detectors in InSb using proton bombardment to create the n‐type layer. At 77 °K, diodes which were 20 mils in diameter had zero‐bias resistances of several hundred thousand ohms. The peak detectivity at 4.9 μ of these diodes with a 2π, 300 °K background was typically greater than 3×1010 cm Hz1/2/W with the largest value observed being 1011 cm Hz1/2/W. Diode quantum efficiencies near 35% were observed.

Schottky barrier InxGa1−xAs alloy avalanche photodiodes for 1.06 μm

Uniform Schottky barrier avalanche photodiodes with gains greater than 250, rise times less than 200 psec, and good quantum efficiencies at 1.06 μm have been fabricated in InxGa1−xAs alloys. The material used for these devices was grown epitaxially on GaAs substrates using an AsCl3–H2–Ga–In vapor‐phase system which permitted grading the epitaxial layers from GsAs to the desired composition.

High‐efficiency ion‐implanted lo‐hi‐lo GaAs IMPATT diodes

A dc‐to‐rf conversion efficiency of 37% combined with an output power of 3.4 W at 3.3 GHz has been obtained from a Schottky‐barrier GaAs IMPATT diode having a lo‐hi‐lo profile. The donor spike or clump was produced by implanting silicon into an epitaxial layer with a n‐type concentration of 1.65×1015 cm−3. Pyrolytic Si3N4 was used to encapsulate the GaAs during the postimplantation anneal. For these devices, the Si3N4 deposition procedure was found to be critical and had to be optimizied to achieve reproducible results. The devices have had very uniform electrical characteristics, and a large yield of devices with greater than 30% efficiency has been obtained. These results indicate that implantation can be used to produce lo‐hi‐lo IMPATT’s with significantly higher device yields than have been obtained by epitaxial techniques.

p‐n Junction Photodiodes in PbTe Prepared by Sb+ Ion Implantation

n‐p junction photovoltaic detectors in PbTe have been fabricated using Sb+ ion implantation to create the n‐type layer. At 77 °K, 15‐mil square diodes have had zero‐bias resistances as high as 15 MΩ for a resistance‐area product of 2.1×104 Ωcm2. Peak detectivities at 4.4 μm in reduced background as high as 1.6×1012 cmHz1/2/W were observed. Diode quantum efficiencies were typically 40% at 4.4 μm.

GaAs SCHOTTKY BARRIER AVALANCHE PHOTODIODES

Uniform avalanche Schottky barrier photodiodes have been fabricated by plating a thin layer of platinum on GaAs and forming a guard ring by proton radiation. Operating at a gain of 100 these photodiodes exhibit gain‐bandwidth products greater than 50 GHz and enhanced signal to noise ratio in excess of 30 dB. The observed variation on the spectral response with bias can be accounted for by a change in the absorption of the Schottky barrier diode.

MIS electroluminescent diodes in ZnTe

Abstract We have observed that proton bombardment can be used to create high resistivity layers in p -ZnTe and have used this technique to fabricate avalanching MIS electroluminescent diodes. The breakdown voltages for these diodes ranged from approximately 6V for 50 keV proton bombardments to 80V for 400 keV proton bombardments. Diodes with a red spectral output as well as diodes emitting in the green luminescent band of ZnTe have been obtained. The red electroluminescence appears to be due to an oxygen isoelectronic trap. The external quantum efficiency of the green diodes is 2×10 −4 at room temperature and 10 −3 at 77°K. That of the red diodes is 3×10 −3 at room temperature and 4×10 −3 at 77°K.

Pb1−xSnxTe photovoltaic diodes and diode lasers produced by proton bombardment

Abstract N-p junction photovoltaic detectors in Pb0.88Sn0.12Te and laser diodes in both PbTe and Pb0.88Sn0.12Te fabricated using proton bombardment to create the n-type layer are reported. Zero-bias resistance area products as high as 1.4 Ω-cm2 at 77°K and 966 Ω-cm2 at 15°K were observed for 15-mil-square Pb0.88Sn0.12Te photodiodes. At 77°K, peak detectivities at 7.5 μm as high as 2.5 × 1010 cmHz1 2 /W were measured. At 15°K, the peak detectivity occurred at 10.2 μm and in reduced background was greater than 10 12 cmHz1 2 / W . Both PbTe and Pb0.88Sn0.12Te laser diodes operated CW at 4.2°K. The PbTe diodes exhibited single mode CW laser operation up to at least 50°K and pulsed operation up to at least 80°K.

PbS photodiodes fabricated by Sb+ ion implantation

N-p junction photodiodes in PbS have been fabricated using Sb+ ion implantation to create the n-type layer. At 300°K, 15-mil-square diodes have shown typical zero-bias resistances of 200 Ω corresponding to a resistance-area product of 0.28 Ω-cm2. At 195°K, the zero-bias resistance increased to 50 kΩ for a resistance-area product of 70 Ω-cm2, and at 77°K, the zero-bias resistance was 5 × 109 Ω for a resistance-area product of 7 × 106 Ω-cm2. Peak detectivities occurred at 2.55, 2.95, and 3.4 μm at 300°K, 195°K and 77°K, respectively. The corresponding measured detectivities were 4.8 × 109, 1.1 × 1011 and 4.2 × 1012 cm Hz12/W. The 77°K detectivity was measured in a reduced background and was amplifier noise limited. Peak quantum efficiencies were typically 50–60 per cent.