The strain energy density in epitaxial overlayers depends strongly on the substrate's surface orientation. The affect of a growth orientation dependent strain energy contribution to the phase stability was studied by growing overlayers of metastable, semiconducting a-Sn films on the (100) and (111) surfaces of Cd0.8Zn0.2Te substrates. On the (100) surface the α-phase of Sn remains stable for coverages up to and beyond 125 ML. On the (111) surface though, the Sn overlayer shows metallic behavior from a partial α→β phase separation for coverages lower than 100 ML. Static calculations using the stress-strain relationship bear out these experimental results by showing that the strain energy density for the (111) growth direction is 38% larger than for the (100) direction.

We studied the influence of visible light on the ZnS/anodic sulfide/HgCdTe interface.

We measured flatband voltage of metal-insulator-semiconductor diodes with semitransparent electrodes at 77 K. In the dark (i.e., without visible light). The flatband voltage of an metal-insulator-semiconductor diode is 0 V. We scanned visible light from 400 to 800 nm and measured the flatband voltage using the photocapacitance measurement. After an initial positive shift, the flatband voltage moved negative by as the wavelength shortened. We studied the relationship between the flatband voltage shift and photon energy using Fowler plots. Results suggest one electron trap level 1.5 eV above the valence band and two hole trap levels 1.7 and 2.3 eV below the conduction band.

ZnS/anodic sulfide films on mercury cadmium telluride, studied using photoluminescence spectroscopy, showed broad photoluminescence peaks at 1.5, 1.7, and 2.3 eV, and the edge emission of the anodic sulfide.

These results suggest that photoionization of the electron trap and two hole traps in the ZnS/anodic sulfide film causes the flatband shift.

The formation of high resistivity (> 107 Ω□) regions in GaAs-AlGaAs HBT and SEED structures by oxygen and hydrogen ion implantation is described. Multiple energy implants in the dose range 1013 cm−3 (for O+) and 1015 cm−2 (for H+), followed by annealing around 500°C are necessary to isolate structures ∼2 μm thick. In each case, the evolution of the sheet resistance of the implanted material with annealing is consistent with a reduction in hopping probabilities of trapped carriers between deep level states for temperatures up to ∼600°C, followed by significant annealing of these deep levels. A comparison of the relative thermal stability of O+ or H+ ion implantisolated p+ material is given. Small geometry (2 × 9 μm2) HBTs exhibiting current gain of 44 and cut-off frequency fT as high as 45 GHz are demonstrated using implant isolation.

A modular spectroscopic ellipsometer for in situ and ex situ materials analysis is described, and results for in situ MBE growth of GaAs/AlGaAs are reported.

In this paper we studied the thermoelectric power under classically large magnetic field (TPM) in quantum wells (QWs), quantum well wires (QWWS) and quantum dots (QDs) of Bi by formulating the respective electron dispersion laws. The TPM increases with increasing film thickness in an oscillatory manner in all the cases. The TPM in QD is greatest and the least for quantum wells respectively. The theoretical results are in agreement with the experimental observations as reported elsewhere.

We study the photomission from ternary and quanternary alloys systems by formulating the respective expressions considering the spin & broadening of Landau levels. It is found taking n-Hg1−x CdxTe and In1−xGaxAsyP1−y lattice matched to InP as examples of ternary and quaternary alloys respectively that the photoemission exhibits oscillatory magnetic field dependence and increases with increasing electron concentration in spiky manner for both the cases. The numerical magnitudes of photoemission in ternary alloys are greater than that of the quaternary systems and the theoretical formulations are in agreement with the experimental observations as reported elsewhere.

Extrinsic far-infrared photoconductivity in thin high-purity germanium wafers implanted with multiple-energy boron ions has been investigated. Initial results from Fourier transform spectrometer(FTS) measurements have demonstrated that photodetectors fabricated from this material have an extended longwavelength threshold near 192μm. Due to the high-purity substrate, the ability to block the hopping conduction in the implanted IR-active layer yields dark currents of less than 100 electrons/sec at temperatures below 1.3K under an operating bias of up to 70mV. Optimum peak responsivity and noise equivalent power(NEP) for these sensitive detectors are 0.9A/W and 5×10−16 W/Hz1/2 at 99μm, respectively. The dependence of the performance of devices on the residual donor concentration in the implanted layer will be discussed.

Recently manganese substituted I-III-VI2 compounds have been investigated. Their magnetic properties are similar to the paramagnetic transistion metal ion substituted II-VI materials, but their crystal structure is non-cubic resulting in anisotropies in their physico-chemical properties that do not exist in the zincblende structure diluted magnetic semiconductors (DMS) materials. In this paper, we report the phase relations on the pseudobinary cut CuInTe2-MnIn2Te4 based on x-ray diffraction and differential thermal analysis data. The range of chalcopyrite structure alloys of composition Cu1−xMnx□xIn2Te4 is limited to x<0.52 due to an eutectic at x=0.74, T= 734°C. A second eutectic exists at x = 0.97, T = 737.5°C. A heretofore unknown congruently melting compound exists in between the two eutectics at x= 0.85, Tm = 760°C. Also, the thus far unknown melting point of the compound MnIn2Te4 was determined (740°C ). Based on the analyses of the first to freeze parts of directionally solidified melts in this range of liquidus compositions by inductively coupled plasma emission spectroscopy the solidus is constructed.

Ellipsometric measurements are extremely sensitive (on the monolayer scale) to layer thicknesses and surface or interfacial roughness. However, lateral resolution is poor, because of the need for a highly collimated ( ≤0.05° ) and therefore large diameter (typically 1 mm) optical beam. Many materials are inhomogeneous on a smaller lateral scale, in which case conventional ellipsometry simply measures some average value. Focusing the beam leads, for an incoherent light source, to an uncollimated beam and a consequential spread in the angle of incidence, which in turn degrades the sensitivity. We describe here a technique for focusing a coherent, Gaussian laser beam to a minimum spot size of about 30μm × 130μm, while maintaining a negligible effective spread in angle of incidence. The technique was used to measure semi-insulating (S.I.) GaAs, laser annealed ion implanted GaAs, and InI Ga1−xAs strained layer structures.

The optical and spectroscopy properties of Il-VI wide gap semiconductor SLSs have been studied. We report the first observation of the pulse compression in ZnS-ZnSe MQW and the folded LA phonon modes in ZnS-ZnSe SLS;The confined LOn phonon modes in ZnSe-ZnTe SLS are observed and the critical thickness of ZnSe-ZnTe SLS are determined,for the first time, by Raman scattering.

A detailed study of local phonon heating due to multiphonon recombination process is presented. Nonequilibrium distribution of defects by vibration energy is calculated taking into account the dependence of capture and emission rates on the defect energy. It is shown that multiphonon generation and recombination of electron-hole pairs stimulate diffusion of defects in energy space. The results are used to calculate the rate of recombination-enhanced defect annealing.

We have grown, fabricated, and measured GaAs quantum well infrared photodetectors (QWIPs) using organometallic vapor phase epitaxy (OMVPE). The epitaxial layers were characterized by electrochemical capacitance-voltage profiling, double-crystal X-ray diffraction, cathodoluminescence, and infrared absorption. Dark current, responsivity spectra, and detectivity were measured for the QWIP devices. The performance of these QWIPs was comparable to detectors grown using MBE. This is of importance since OMVPE has advantages for wafer throughout and cost.

Near-surface damage created by Ar+ ion milling in InP and GaAs was characterized by capacitance-voltage, current-voltage, photoluminescence, ion channeling and transmission electron microscopy. We find no evidence of amorphous layer formation in either material even for Ar+ ion energies of 800eV. Low ion energies (200eV) create thin (≤100 Å) damaged regions which can be removed by annealing at 500°C. Higher ion energies (≤500 eV) create more thermally stable damaged layers which actually show higher backscattering yields after 500°C annealing. Heating to 800°C is required to restore the near-surface crystallinity, although a layer of extended defects forms in GaAs after such a treatment. No dislocations are observed in InP after this type of annealing. The electrical characteristics of both InP and GaAs after ion milling at ≥500 eV cannot be restored by annealing, and it is necessary to remove the damaged surface by wet chemical etching. For the same Ar+ ion energies the damaged layers are deeper for InP than for GaAs-after 500 eV ion milling at 45° incidence angle, removal of ∼485 Å and ∼650 Å from GaAs and InP respectively restores the initial current-voltage charaeteristics of simple Schottky diodes.

High mobility of electrons, the possibility of formation of semi-insulating layers excites an interest to GaAs. The implantation of donor impurities into semi-insulating GaAs:Cr has a great practical application, allowing to create the conducting suhnicrcn layers. To obtain the functional suhmicron n+-layers one uses mainly the implantation of ions of Si, that accounts for its small mass and the lack of the necessity for irradiation at higher teMperatures. Silicon is the amphoteric impurity in GaAs. At low doses ≤1013 Cm−2 it behaves as donor inpurity with the high level of activation, though at the increase of the implantation dose some of the siliccn atoms begin to substitute arsenic and in this position they display the properties of acceptor impurity, leading to self-compensation. Its amphoteric properties were shown with the help of As+Si and Ga+Si double implantation [1]. The increase of activation of Si, as donor impurity, can be obtained by double implantation of 31p+28Si [2]. Phosphorus has atomic mass close to Si, it is isoelectronic to As and does not cause compensation effect in GaAs up to the doses ≃1015 cm−2. Moreover double implantation allows to vary the magnitude of the diffusion coefficients of impurities.

InP and InAs (100) were grown by gas-source molecular-beam epitaxy (GSMBE) with arsine, phosphine, and elemental indium. Reflection high-energy-electron diffraction (RHEED) was used to monitor surface reconstructions and growth rates. (2×4) to (2×1) transition was observed on InP (100) as phosphine flow rate increased. (4×2) and (2×4) patterns were observed for In-stabilized and As-stabilized InAs surfaces, respectively. Both group-V and group-rn-induced RHEED oscillations were observed. The group-V surface desorption activation energy were measured to be 0.61 eV for InP and 0.19 eV for InAs. By this growth rate study, we are able to establish a precise control of V/HII atomic ratios in GSMBE of InP and InAs.

There is a great need of long-wavelength (8-17μm) infrared (LWIR) focal plane arrays (FPAs) for a variety of space and defense applications. Si-based infrared detectors offers several important advantages, including good uniformity, low cost, and easy integration with Si readout circuitry either monolithically or by indium bump bonding to form large arrays. We report here a novel SiGe/Si heterojunction internal photoemission (HIP) long-wavelength infrared (LWIR) detector fabricated by molecular beam epitaxy [1].

Narrow energy band gap semiconductors are potentially useful for various devices, including infrared detectors and diode lasers. Rare earth elements have been introduced into lead chalcogenide semiconductors using the molecular beam epitaxy growth process. Europium and ytterbium increase the energy band gap, and nearly lattice-matched heterojunctions have been grown. In some cases, valence changes in the rare earth element cause doping of the alloy. Some initial investigations of the addition of europium to indium antimonide will also be reported, including the variation of lattice parameter and optical transmission with composition and a negative magnetoresistance effect.