The electrical characteristics of In, Sn, Au and Pt contacts on n-type Hg0.4Cd0.6Te formed in the presence and absence of prior In2+ implantation have been examined. Measurements of specific contact resistance made using a Transmission Line Model have shown that the unimtlanted In/Hg0.4Cd0.6 and Sn/Hg0.4Cd0.6 junctions gave values of pc = 3.0x10−3 to 4.0x10−3 ohm.cm2. Auger sputter profiles of the asdeposited In/Hg0.4Cd0.6 and Sn/Hg0.4Cd0.6 interfaces have shown a significant in-diffusion of the metal overlayer. The influence of shallow In2+ implantation prior to metallization was an increase in pc which occurred above a dose of 1013 ions/cm2. In contrast, Pt and Au formed Schottky barrier diodes on n-type Hg0.4Cd0.6 with øb=0.69eV for Pt and øb=0.79eV for Au. With prior In2+ implantation, both Pt and Au contacts exhibited an ohmic behaviour with pc= 2x10−1 ohm.cm2. These results have significance in the fabrication of devices for 1.0 -2.5μm optical communications.

An overview is provided of long wavelength, photovoltaic detectors constructed with type II (also known as “staggered”), III-V superlattices. Specifically, the electronic properties of InAsSb strained-layer superlattices and prototype detectors utilizing these structures are described.

GaSb, AlxGa1-xSb, and AlxGa1-xSb epitaxial layers were grown by the liquid-phase epitaxy and characterized by photoluminescence, Raman spectroscopy, and double-crystal X-ray diffraction. The concentration of residual acceptors which are related to structural defects decreased with lowering growth temperature, but the GaSb epitaxial layer grown at an extremely low temperature of 270°C had poor crystalline quality. The AlxGa1-xSb (x≥0.15) and AlxGa1-xSb (x=0.02) epitaxial layers grown at 270 °C, however, had much better quality than the GaSb epitaxial layer grown at the same temperature.

Infrared absorption and photoluminescence have been demonstrated for InAs1-xSbx/InSb strained-layer superlattices (SLS's) in the 8-15 μm region for As content less than 20%. This extended infrared activity is due to the type II heterojunction band offset in these SLS's. The preparation of the first MOCVD grown p-n junction diode was achieved by using dimethyltellurium as an n-type dopant. Several factors, such as background doping and dopant profiles affect the performance of this device. InSb diodes have been prepared using tetraethyltin. The resulting current-voltage characteristics are improved over those of diodes grown previously using dimethyltellurium. Doping levels of 8x1015 to 5x1018cm−3 and mobilities of 6.7x104 to 1.1x104 cm2/Vs have been measured for Sn doped InSb. SLS diode structures have been prepared using Sn and Cd as the dopants. Structures prepared with p-type buffer layers are more reproducible.

InAs and InAs0.85Sb0.15p-“i”-n structures were grown on InAs, GaAs and Si substrates by Molecular Beam Epitaxy. The structural quality of the layers is discussed using Transmission Electron Microscopy and Rutherford Back Scattering. The influence of the material quality on the 77 K current-voltage measurements is explained. The spectral response of the devices was measured demonstrating peak responsivities of 2.1 A/W at 3.5μm wavelength for InAs0.85Sb0.15 detectors with a 4.3 μm cut-off wavelength.

In this paper we reported most attractive semiconductor materials for optical sources and detectors with wavelength In the range of 2-4 μm, such as GaInAsSb/GaAlAsSb, InAsPSb/InAs heterostructure and PbCdSSe HgCdTe.The Lasers and detectors have been made using these materials. The performance of the devices were discussed.

Photol uminescence of p-P InAs/InAsPSb and InAs/InAl AsSb heterojunctions grown by LPE method was studied at liquid helium temperature. The recombination spectra contained a new broad band lying between the substrate and the layer lines which was identified as an emission from the interface. This line is characterized by a strong blue shift when the excitation intensity increases. The intensities of bulk and interface lines show an unusual dependence on the pumping power. On the basis of experimental findings the interface line is attributed to emission from electrons confined at the interface due to reflection of elecctrons moving above the barrier.

The band gap of InAsSbP and InGaAsSb alloys enriched with InAs correspods to the spectral range 2.5 - 5 μm which make possible to manufacture LEDs and detectors for the second atmosphere window. Elevated hardness (see Fig.1a ) and small plasticity of the alloys results in an inversed plastic deformation process during LPE growth of InAsSbP (InGaAsSb) on InAs substrate.That is when growing graded( grad a ≈5*10−8 epilayers at elevated temperatures ( 680 - 720° C ) misfit dislocations are formed throughout the entire substrate thickness (C). Simultaneously with increasing dislocation density in InAs ( curves 1,3 ), the curvature of the structure increased within æ = 0.02-0.2 cm−1.

Molecular beam epitaxy has been used to grow GaInAsSb/AlGaAsSb double heterostructures, lattice matched to GaSb substrates, for diode laser emission at 2.3 μm. Doublecrystal x-ray diffraction measurements were used to determine alloy lattice constants, and photoluminescence and infrared absorption spectroscopies were used to determine the bandgaps of the GaInAsSb layers. Alloy compositions measured by Auger electron spectroscopy were consistent with measured lattice constants and bandgaps. Diode lasers fabricated from the double heterostructures were operated in the pulsed mode at room temperature with threshold current densities as low as 1.5 kA cm−2, differential quantum efficiencies as high as 50 percent, and output power as high as 900 mW per facet.

The infrared optical absorption properties near and above the fundamental absorption edge of MBE grown undoped GaInAsSb quaternary semiconductor alloy deposited on GaSb and GaAs substrates have been measured and analyzed at room temperature by means of a Fourier Transform Infrared Spectrometer, and were found to be fully characterized by the interband transition theory and Urbach's rule. The optical band gap of MBE-GaInAsSb has been determined using a linear extrapolation of (ɑhv )2 as a function of the photon energy hv, and the refractive index n deduced from the interference pattern, which shows good agreement with the theory of Sadao Adachi's.

30 nm thick layers of Be-doped InSb were grown by MBE, sandwiched between undoped layers of InSb on semi-insulating GaAs substrates. Using secondary ion mass spectroscopy (SIMS), it has been demonstrated that the p-type dopant, Be, undergoes an anomalous migration towards the top surface for substrate growth temperatures in excess of 340°C. A thermal diffusion process can be eliminated as an explanation since there was not an associated diffusion towards the substrate. At a substrate growth temperature of 340°C, the Be-doped layer had backside and frontside doping concentration gradients of 0.067 and 0.147 decade/nm. respectively. A sample grown at 420°C had a comparable backside doping concentration gradient, but the frontside gradient was essentially zero, i. e., uniform doping tothe surface. Electrical activation of the Be dopant, when grown at 340°C, compared to activation in GaAs grown at 580°C. was 38% and 47% for growth rates of 1.0 and 0.5 μm/h. While the Si dopant does not undergo a migration comparable to that of Be, it has been demonstrated that n-type doping of InSb with Si must be done at growth temperatures less than or equal to 340°C to obtain high carrier concentrations. The maximum n-type carrier concentration obtained was 6.2x1018/cm3, for a 0.5 μm/h growth rate at 340°C.

Multilayer InSb/CdTe and InSb/MnTe heterostructures are grown by molecular beam epitaxy. The analysis of multilayer structures by transmission electron microscopy (TEM) and x-ray rocking curves confirms the presence of periodic heterointerfaces. TEM, x-ray, and x-ray photoelectron spectroscopy (XPS) measurements are found to provide a sensitive indicator for the presence of ultra-thin interfacial layers. Double barrier structures in the MnTe/InSb/MnTe configuration exhibit the negative differential resistance which is characteristic of resonant tunneling diodes.

Low pressure (200 Torr) metalorganic chemical vapor deposition (MOCVD) of InSb has been examined through variation of the Column III (TMIn) and Column V (TMSb or TESb) precursor partial pressures. The use of lower growth pressure significantly enhanced the range of allowable Column III and Column V partial pressures in which specular morphology InSb could be obtained without the formation of In droplets or Sb crystals. In addition, a 70% improvement in the average hole mobility was obtained, compared to InSb grown in the same reactor at atmospheric pressure. SIMS analysis revealed that Si at the substrate/epitaxial layer interface is an important impurity that may contribute to degradation of the mobility. Substitution of TESb for TMSb did not result in any improvement in the purity of the InSb.

To date, OMVPE has failed to grow epitaxial InSb at temperatures below about 400 °C. Therefore, we have studied InSb deposition using the novel group V source triisopropylantimony (TIPSb) with trimethylindium (TMIn), comparing this with results in the same reactor using trimethylantimony (TMSb). We have grown InSb on both GaAs and on high-resistivity p-type InSb substrates, exploring the effects of temperature, substrate, V/ill ratio, and thickness on film properties. Our best results with TMSb and TMIn were obtained using a V/ill ratio of 8 and growth temperature of 450 °C. The unintentionally doped films exhibited good crystallinity and were n-type about lx1015 cm-3 down to 5 K, with 77 K mobilities of 90,000 and 253,00°Cm2/V-sec for InSb on GaAs and on InSb, respectively. These results are comparable to the best published MBE data. While InSb films could not be grown well at temperatures below 425 °C using TMSb, specular epilayers were obtained with TIPSb at temperatures as low as 300 °C, though with a low deposition rate. Our best conditions with TIPSb were with a Vill ratio of about 12 and a substrate temperature of 350 °C. The results of variable temperature and variable magnetic field Hall, double crystal x-ray diffractometry, Nomarski microscopy, Auger electron spectroscopy and scanning electron microscopy will be presented.

Heteroepitaxial (100)CdTe || (100)InSb structures have been fabricated by growing CdTe epilayers, at growth temperatures below 200°C, on single crystal InSb substrates by low-energy bias sputtering. Controlled low-energy ion bombardment at the substrate was employed to clean the growth surface in-situ just prior to film deposition and to modify the growth kinetics and enhance adatom mobility during deposition. Raman spectroscopy of the interface revealed no evidence of In2Te3 and secondary ion mass spectroscopy showed the interface to be chemically abrupt.

-Although a variety of novel device proposals for GaSb/(Al,Ga)Sb/InAs heterostructures have been made, relatively little is known about processing these materials. We have studied the reactive ion etching characteristics of GaSb, (AI,Ga)Sb, and InAs in both methane/ hydrogen and chlorine gas chemistries. At conditions similar to those reported elsewhere for RIE of InP and GaAs in CH4/H2, the etch rate of (AI,Ga)Sb was found to be near zero, while GaSb and InAs etched at 200Å/minute. Under conditions where the etch mechanism is primarily physical sputtering, the three compounds etch at similar rates. Etching in Cl2 was found to yield anisotropic profiles, with the etch rate of (AI,Ga)Sb increasing with Al mole fraction, while InAs remains unetched. Damage to an InAs “stop layer” was investigated by sheet resistance and mobility measurements. These etching techniques were used to fabricate a novel InAs-channel FET composed of these materials. Several scanning electron micrographs of etching results are shown along with preliminary electrical characteristics.

Be, S, Si, and Ne implantations were performed at room temperature into InSb layers grown on undoped semi-insulating GaAs substrates. The implant damage in InSb is of ntype behavior. The implanted material was subjected to both isochronal and isothermal annealing schemes using a molybdenum strip heater. A maximum p-type activation of 90 % and si-type activation of 16 % was achieved for Be and S implants, respectively. Si implant has an amphoteric doping behavior.

The growth reaction mechanism was experimentally investigated for TEGa and TMSb used for MOCVD GaSb epitaxial growth. The variations of growth rate, substrate temperature, the V/III ratio and the mole-fraction of III and V source gases, were detailly considered and investigated with regard to their effect on electrical and optical properties were measured during the epitaxial process. The experimental results were used to provide an inspection on defects interaction mechanisms and on the type of conductivity. Based on the investigation of growth mechanism, at 470°, a high quality GaSb epitaxial film 1 with 3 mobility, 634 cm2/V*sec and low hole concentration, 1.67x1016 cm−2 was obtained.

Undoped GaSb epilayers have been grown on (100) GaSb and S.I. GaAs substrates. The effects of growth temperatures and TMSb/TEGa mole fraction ratios on the epitaxial properties of surface morphology, growth rate, hole concentration and mobility (300K and 77K) have been studied. The lowest concentration 1.8x101 6 cm- 3 (77K) and the highest mdobility 1447 cm2/V.s (77K) can be obtained under V/III ratio of 6.64 at 550°C. Photoluminescence intensity was found to be a function of the V/III ratios. When V/III ratios increased or decreased beyond 6-8, the BE peaks disappeared and PL spectra became roughened.

To reduce the effects of large lattice-mismatch in highly strained GaSb/GaAs system (7% mismatch) on the electrical properties, a 10-period In0.3Ga0.7As/GaAs (60A/40A) strain layer superlattice (SLS) has been grown on GaAs substrates as a dislocation filter before the GaSb epitaxial growth. From the comparison of 77K Hall mobility of GaSb/GaAs as a function of growth temperature with that of GaSb/SLS/GaAs, it was clearly observed that the epilayers grown on SLS structures have higher mobility than those grown directly on GaAs substrates. From the TEM analysis, we observed that all dislocations propagated up to the GaSb epilayer surface in the GaSb/GaAs system but some of the dislocations bending before reaching the epilayer surface in the GaSb/SLS/GaAs system.

Dry etching of HI-V materials using both Cl-based (CCl2F2, SiCl4, BCl3, Cl2) and CH4/H2 discharges will be reviewed. The etch rates using chlorine-based mixtures are generally faster than those utilizing CH4/H2, but the latter gives smoother surface morphologies for In-containing compounds. The use of microwave (2.45 GHz) electron cyclotron resonance (ECR) discharges minimizes the depth of lattice disorder resulting from dry etching, relative to conventional RF (13.56 MHz) discharges. Recent results on the systematics of ECR plasma etching of both In- and Ga-based III-V semiconductors using CCl2F2/O2 and CH4/H2 mixtures will be discussed, including the determination of the maximum self-biases allowable which do not induce near-surface damage to the semiconductor. A further key issue is the prevention of changes in the surface stoichiometry of materials such as InP, where the lattice constituents may have considerably different volatilities in the particular discharge.