This paper reviews some key areas where MeV ion beams can be applied to III-V semiconductor materials. In particular, ion damage is assessed for various III-V materials in terms of implantation parameters, especially substrate temperature and dose rate. Implant isolation, involving the introduction of damage to remove carriers and achieve highlyresistive layers, is assessed for MeV irradiation. It is concluded that MeV ions can provide deep, uniform damage with a single-energy implant. Finally, improved epitaxy of amorphous InP with MeV ions is demonstrated.

Pt/Ti contact to variety of binary III-V and related ternary semiconductor materials were established. These contacts were formed by electron beam evaporation and subsequent rapid thermal processing in order to sinter the metal-semiconductor systems. The contacts to p-type InAs, GaAs, In0.53Ga0.43As, In0.52Al0.4As and Ga0.7Al0.3As were ohmic, as a result of heating at temperatures of 450°C or higher. The Pt/Ti contacts to InP and GaP displayed Schottky behavior as-deposited and preserved the rectifying nature through heat treatments, regardless of the processing conditions. The electrical properties and the microstructure evolution in these 7 systems is discussed in this paper.

Low pressure MOVPE in a horizontal reactor has proven to be capable of yielding uniform InP, GalnAs and GaInAsP layers [1, 2]. However, the complexity of some devices as MQW lasers and HEMTs require even further improvement in thickness and compositional uniformity. This can be achieved by using the technique of sub-strate rotation to overcome gas phase depletion problems and geometry related non uniformities.

This paper reviews the current status of material issues in the InGaAs(P)/InP system and our understanding of degradation in InGaAsP/inP double-heterostructure lasers and LED's.

Among the materials issues for this system are the generation of defects and the thermal stability of the material. Crystal growth-induced defects can be classified into interface and bulk defects.; the former group includes misfit dislocations and inclusions and the latter structural and non-structural precipitates. Thermal stability can lead to structural imperfections stuch as quasi-periodic modulated structure due to spinodal decomposition of the crystal either at the liquid/solid interface or growth surface, and atomic ordering which also occurs on the growth surface through migration and reconstruction of deposited atoms. Diffusion processes in InP often lead to the generation of microdefects in this material. Finally, in metallization procedures, alloy reactions between the semiconductor and electrode occasionally take place forming non-planar/non-uniform interfaces.

Three major degradation modes, rapid degradation, gradual degradation, and catastrophic failure in InGaAsP/InP double-heterostructure lasers and LED's, are discussed. For rapid degradation, recombination-enhanced dislocation climb and glide, which are responsible for degradation, do not occur easily InGaAsP/JnP system. Differences in the ease with which these phenomena occur in InGaAsP/InP and other systems are presented. Based on the results, dominant parameters involved in the phenomena are discussed. Gradual degradation takes place presumably due to recombination enhanced point defect reaction in GaAlAs/GaAs-based optical devices. However, we do not observe this mode in InGaAsP/InP-based optical devices. Catastrophic failure due to catastrophic optical damage at a mirror or at a defect in GaAlAs/GaAs DH lasers, is not found in InGaAsP/lnP DH lasers. Degradation of InGaAsP/InP double-heterostructure LED's with large current application is also presented. These results indicate that InGaAsP/InP optical devices ensure very high reliability in longwavelength communication systems.

Determining the composition of quaternary epitaxial films requires accurate measurements of both the lattice parameter and the bandgap energy. Complications arise in lattice-mismatched material, because the mismatch produces tetragonal distortion of the epi-layer and splitting of the valence band energies in a manner which depends on the film composition. We present studies on strained InGaAsP grown on (100) InP. Using room temperature photoreflectance (PR) we observe shifting of the band gap and splitting of the valence band energies, and using the (115) and (004) reflections from double crystal x-ray diffraction (DXRD) we determine the values of the parallel and perpendicular lattice constants. By combining the lattice parameter measurements with band splitting data, we accurately determine the quaternary composition from a self-consistent model using an iterative procedure. By linear interpolation of the elastic-stiffness constants, C11 and C12. as well as the shear and hydrostatic deformation potentials for the four binary compounds in the InGaAsP system, we relate the state of biaxial stress to the induced shifts in the valence band energies.

The linewidth and peak position (vo) of the intersubband transition (IT) in GaAs/Al0.3Ga0.7As multiple quantum wells are studied as a function of temperature using the infrared absorption technique. We find that electrons in the GaAs well are weakly coupled to the GaAs normal optical phonon mode. The total integrated area of IT absorption is found to be approximately constant in the samples that were doped in the well but temperature dependent in the samples that were doped in the barrier. We also find that vo increases as the temperature decreases. This blue shift is found to increase as the dopant concentration is increased. We calculated the absorption spectrum in a nonparabolic-anisotropic envelope function approximation including temperature dependent effective masses, nonparbolicity, conduction band offsets, the Fermi level, and lineshape broadening. Our results indicate that a large manybody correction, in particular an exchange interaction (Eexch) for the ground state, is necessary to account for the observed blue shift as the dopant concentration increases.

Utilizing infrared absorption and Hall measurements, a detailed study is presented of the temperature dependence (10 K < T < 300 K) of the intersubband transition and related doping behaviour in GaAs/Al0.32Ga0.68As multiple quantum well structures with Si doping concentrations between 1×1018 and 8×1018 cm−3 in the quantum wells. The intersubband transition frequency increases with decreasing temperature, which can be adequately modelled by considering the different effective masses and the thermal populations of the two electron subbands. This model also accounts for the decrease in linewidth of the infrared absorption resonance upon cooling. In Hall measurements a persistent photo-induced decrease in the free electron concentration within the GaAs quantum wells is observed for Si doping levels exceeding 5×1018 cm−3. Corresponding decreases are observed both in the integrated absorption and the absolute frequency of the intersubband transition, the latter arising from a reduction in the depolarization shift. The spectral dependence of the photo-induced changes over the energy range 1.2 eV < hν < 2.5 eV, along with thermal regeneration over the temperature range 70 K < T < 150 K, have been studied.

The quaternary GaxIn1−xAsyP1−y semiconductor alloy system has considerable importance for present day optoelectronic and microwave device applications. For state of the art high mobility samples grown by metal organic chemical vapor deposition (MOVPE) there are few experimental techniques which both can asess band structure related properties (effective mass m*, g-values of free electrons) and impurity related properties (luminescence, mobility and lifetimes). In this paper we compare optical and transport properties of the quaternary compound GaxIn1−xAsyP1−y, (x=0.47,y-l; x=0.42,y=0.92; x=0.28,y=0.61; x=0.12,y=0.34) lattice matched to*{nP by optically detected magnetic resonance techniques.

0.15µm epilayers of InxGa1−xAs grown on GaAs (001) by MBE, having In concentrations in the range x = 0.05 - 0.30, have been investigated using RHEED and TEM. RHEED patterns indicate a 2-D growth mode for low In concentrations changing to Stranski-Krastanov growth for x > 0.30. TEM showed misfit dislocations for x > 0.05 only, which were found to relieve only a small part of the misfit strain. Although threading dislocations were rarely found in the epilayers, dislocations originating at the interface and penetrating the buffer layer were observed for 0.1 < x < 0.25.

TBA and TBP are attractive candidates for group V sources for MOVPE growth from the viewpoint of safety. We studied how the composition of InGaAsP crystals depends on growth conditions, and investigated its electrical and optical properties. The relationship between group V sources and crystals indicates that TBA and TBP decompose into AsH and PH. Since there is no carbon in AsH and PH, carbon contamination in the crystals is expected to be small. Carrier concentrations ranged from 5×1014 cm−3 to 1.5×1015 cm−3. Photoluminescence spectra at 4.2K showed strong band-edge emission with no acceptor-related emission. Based on the electrical and optical properties of the crystals, we conclude that high-quality InGaAsP crystals can be grown using TBA and TBP.

We review MBE growth of epitaxial IV-VI layers on Si(111) substrates and fabrication of photovoltaic infrared devices in the layers. Cut-off wavelengths are chemically tailored from 3 µm up to above 12 µm by using PbS, PbTe, Pb1−xEuxSe and Pb1−xSnxSe. An intermediate epitaxial stacked CaF2-BaF2 bilayer of 200 nm thickness serves to overcome the large lattice- and thermal expansion mismatch, and device quality IV-VI layers are obtained with layer thicknesses of only 2–4 µm. The layers are untwinned single crystal, exhibit perfectly smooth surfaces with surface defect concentrations down to 103 cm−2, and x-ray rocking curve line-width of ≈150 arcsec. Despite the large thermal expansion mismatch, the (111)-oriented layers withstand multiple cooling cycles down to 15K without problems.

Although our IR-device fabrication technique is far from optimized, the sensitivities of our best photovoltaic sensors are comparable to MCT. IV-VI on Si IR sensors have the potential for a low cost technique of large IR focal plane arrays both for the 3–5 µm and 8–12 µm range because of the easy fabrication procedure and because uniformity problems are much less severe in IV-Vls due to the weaker dependence of the band-gap of Pb1−xSnxSe on composition x compared to MCT.

We report the investigation of an interconnect circuit board (ICB) with anisotropic thermal expansion for use with bump bonded, indirect hybrid, scanning focal plane arrays. This ICB is designed to reduce significantly the thermal stresses on the indium bump bonds during thermal cycling. Highly oriented pyrolitic graphite (HOPG) was chosen because its anisotropic thermal expansion meets the criteria for forming an indirect hybrid ICB using silicon processor circuits and mecury cadmium telluride detectors. Properties of HOPG influencing its performance as an ICB have been investigated including thermal expansion, electrical conductivity, durability, and adherence of electrically insulating thin films.

A new method of X-ray diffraction analysis of structural inhomogeneities in the quartz/Si02/n based inorganic glasses is presented. The method enables the determination of structural changes occuring in the real nodal lattice in the regions of 10…20 Å or more as well as substructural changes in the regions 5…15 Å comparable to the molecular size of SiO2…SiO4. In consequence these changes can be correlated with approximate nodal lattice models of different degree of ordering. The applied method provided the possibility of constructing structural models of nodal lattices describing the surface and inner layers of the real glasses, changes in the local inhomogeneities as well as boundaries in water-gel associates.

Some applications for long-wavelength infrared (LWIR) windows require environmental durability and mechanical strength in addition to infrared optical transparency; i.e., the windows must simultaneously serve as optical and as structural ceramics. The requirement of optical transparency at long IR wavelengths eliminates from consideration all ceramics based on oxides and other light-anion compounds, making this a particularly difficult materials problem. The structure-property relationships and chemical rationale used to guide both the screening of known compounds and the synthesis of new compounds likely to possess the desired properties rely on factors such as atomic mass, electronic configuration, coordination number, and crystal structure type.

Our research has included the directed synthesis and characterization of a number of ternary indium sulfides as well as ternary calcium yttrium sulfides. Ternary indium sulfides feature both tetrahedral and octahedral coordination of indium. The crystal structure of KInS2 and its relationship to structures observed in other systems such as AIn2S4, A = Ca,Sr,Ba, is described. The crystal structure of CaY2S4 along with studies of yttrium-doped CaS are also described. The AIn2S4 compounds are more fully described in references [1] and [2].

We measured the far-infrared reflectivity spectra of PbTe(Ga) and Pb1−xSnxTe(In) - materials revealing the Persistent Photoconductivity effect at the low temperatures T<Tc; Tc≈80K and 25K, respectively-The reflectivity spectra display the singuliarity nearby the plasmon-phonon minimum. The spectra may be fitted satisfactory by means of the introduction of an additional oscillator into the dispersion relation. The result is interpreted in the framework of the model taking into account the temperature change of the one-electron metastable impurity state Position in the configuration-coordinate space. The oscillator corresponds to the two-electron - one-electron state transitions. Some previously unexplained results find the satisfactory interpretation in the framework of the model Proposed.

In this paper, the effect of sputtering parameters on the interfacial reaction and the electronic properties of the WNx system were reported.

The report showed that W and W2 N phases were observed in WNx film on GaAs substrate annealed at 800–900°C, in which no UN phase was found and W2N was the stable phase. Throughout the WNx film, W,N distributed uniformly. There was no interdiffusion between WN, films and GaAs substrate annealed at 80°C. However, at 900°C, there was some N in-diffusion to substrate, but no Ga or As out-diffusion. The electrical resistivity p of WNx films increased with increasing nitrogen partial pressure r. All the samples with r<0.2 showed the p below 200 µΩcm. By the I/V measurement, the Schottky Barrier Height was obtained with the value: øB=0.93ev, n=1.30 for WNx/n-GaAs contact that annealed at 850°C, 15 minutes.

Optical properties of Er, Tr, and Pr ion implanted GaAs and A1xGa1−xAs were investigated using photoluminescenoe. For Er, the characteristic sharp emissions around 1.54 μm were observed at sample temperatures as high as 296 K, which are due to the transitions between the weakly crystal-field-split spin-orbit levels 4I13/2 and 4I15/2 of Er3+ (4f11) ; the strongest luminescence signal was from A10.4Ga0 6As. For Tm, the sharp 4f-emissions were observed between 1.22 to 1.33 μm at sample temperatures up to 200 K, and are due to the transitions between levels 3H5 and 3H6 of Tm3+ (4f12). For Pr, three sets of 4f-emissions were observed at 1.05, 1.35, and 1.6 μm due to transitions between levels 1G4∼3H4, 1G4∼3H5, and 3F3 ∼ 3H4 of Pr3+(4f2), respectively, and the highest temperature at which sharp emissions were observed was around 175 K.

An analysis of the temperature dependent mobility in lightly doped ZnSe epitaxial layers grown on a semi-insulating GaAs substrate by Molecular Beam Epitaxy is reported. Our results indicate that the temperature dependence of the mobility is in poor agreement with calculated values based on typical phonon and ionized impurity scattering mechanisms. Good agreement between theory and experimental data call be obtained by including a scattering term associated with the space-charge region surrounding defects.

A TEM study is presented charting the development of a MOVPE growth process for the deposition of CdTe//ZnTe superlattices. In addition, MBE grown (Cd,Zn)Te//CdTe superlattices deposited onto GaAs and InSb substrates are compared.

Approximate methods are used, for a variety of II–VI semiconductor alloys, to estimate the sensitivity to composition change of quantitative transmission electron microscopy techniques which have proved successful in characterising III–V heterostructures. It is shown that bright field thickness fringe matching at the [001] axis is likely to prove relatively more successful than 200 dark field intensity measurement for many alloy systems. It is also noted that alternative methods would be necessary if quantitative characterisation of (Mn,Zn) compounds were required.