The metalorganic chemical vapor deposition (MOCVD) growth of CdTe and HgTe on GaAs (111) and (100) substrates in a vertical, high-speed, rotating-disc reactor was investigated. A range of total reactor pressure, carrier gas flow rate, chemical concentrations, deposition temperature, and rotation rate have been investigated in an attempt to optimize growth conditions. Diisopropyltelluride (DIPTe) and Dimethylcadmium (DMCd) were used as growth precursors. Thickness uniformity varies less than +/- 1.5% over 50 mm diameter wafers. Films having FWHM X-ray rocking curves less than 90 arcsec were obtained on GaAs (111) substrates. The films have excellent surface morphology, exhibiting less than 5x104 cm-2 orange peel dents which are << 1 µm in size. An elemental mercury source was added to the growth system. Initial results for the growth of HgTe and HgCdTe will be discussed in this text.

High-resolution x-ray diffraction (HRXRD) measurements of strained-layer superlattices (SLS's) have been carried out using a four-crystal monochromator. A wide asymmetric range of sharp higher-order x-ray satellite peaks is observed indicating well-defined periodic structures. Using a kinematical diffraction step model very good agreement between measured and simulated x-ray satellite patterns could be achieved. These results show that this x-ray method is a powerful tool to evaluate the crystal quality of SLS's.

Hahn-Meitner-Institut, D-1000 Berlin 39, W. Germany Abstract The transient photoconductivity, in MBE grown silicon doped GaAs films, was studied by a contactless microwave conductivity technique. The dark carrier concentration of the investigated films varies from 4 x 1014 cm-3 to 6 x 1017 cm-3. At least two decay channels can be distinguished. An initial fast decay process (t<20 ns), which is excitation intensity dependent, followed by a slower one. The fast decay is tentativly identified with a direct electron-hole recombination and is more pronounced at high excitation intensities and in low impurity materials. The slower decay component is characterized by effective electron lifetimes ranging from 2 µs for low impurity fims up to 100 µs for high impurity samples. It can be concluded that an increase of the Si-concentration leads to an increase in the concentration of hole traps, which quenches the initial electron-hole recombination and decreases the electron decay rate in the microsecond region.

We present various x-ray diffraction phenomena from semiconductor hetero-epitaxial layers. Each of these phenomena gives useful information on the layers. Knowing what to look for in the x-ray rocking curve (XRC) can make this nondestructive technique a very powerful tool for characterization of a few A-several g.tm thick layers We discuss the use of individual Bragg peak, diffraction fringe, and interference structure to obtain layer information. We particularly emphasize the use of x-ray interference in studying buried strained quantum well or quantum barrier layers. We present experimental rocking curves of an AlGaAs/GaAs double heterojunction laser structure and GaInAs/GaAs strained layer superlattices in both <001> and <111> orientations.

Two methods have been developed for simulating the C-V profiles of semiconductors. Each method uses a different approach to the problem so that, between them, degeneracy, interface charge, deep levels, low temperatures and quantum effects may be included. Computer run times depend on the complexity of the structure being modelled but are generally quite fast. The profile for a typical single heterostructure may be obtained on a desk-top HP200 in less than two minutes.

AlxGa1-xAs films, doped with silicon in the 1 x 1018 cm-3 range, have been prepared in the composition range x = 0.20 - 0.46 by molecular beam epitaxy. The influence of defect states on excess carrier trapping and recombination processes is studied by a contactless transient photoconductivity technique in the microwave region. Effective electron life- times in the 1 x 10-5s range for the 20% Al film down to the 1 x 10-7s range for the 46% Al film were found, indicating a larger density of electron traps in more Al rich films. The decay kinetics in AlGaAs is compared with the decay kinetics in GaAs.

A simple method for determining layer composition and mismatch of semiconductor hetero-epitaxial samples is by measuring the separation of peaks in x-ray rocking curve (XRC). This method fails if the peak separation is affected by other factors. For a small layer thickness, the layer peak position is affected by the x-ray amplitudes of the substrate or other thicker layers through the interference and overlap effects. In this case, a diffraction theory fitting process is necessary for a correct determination of layer parameters. We have used dynamical and kinematical x-ray diffraction theories to calculate the layer peak position as a function of its thickness for various layer/substrate combinations. These two theories yield substantially different results, indicating that the kinematical diffraction theory analysis is no longer valid for these thin layers. When a thick layer is present along with the thin layer, the thick layer is more influential than the substrate to the thin layer peak position, making the dynamical theory fitting necessary even from higher thickness.

We carried out the photoluminescence measurements at low temperature for Be-doped GaAs. Samples were grown by molecular beam epitaxy and Be con- centration was varied by controlling the cell temperature of Be. Besides the well-defined emission, [g-g], which is observed for the acceptor con- centration [A] from ∼ 5x1016 cm-3 to ∼ 1x1018 cm-3 and which shows steep red shift with increasing [A], we observed two unusual emissions temporarily denoted by [g-g]α and [g-g]β. These emissions were commonly observed just below bound exciton emissions for heavily-doped region of [A]>1x1018 cm-3. [g-g]α indicated a strong blue shift with increasing [A] and its energy can become larger than the direct band-gap energy of undoped GaAs at 2K when [A] exceeds 5x1019 cm-3. On the other hand, [g-g]β was observed in the vicinity of the band-to-acceptor emission and showed red shift with increas- ing [A]. We here proposed a model that these two emissions are attributed to the binding states of acceptor-acceptor pair formed by the overlapping of the wave functions in the ground state of an isolated acceptor. This situation is principally different from that of [g-g] in which the formation of acceptor-acceptor pair was ascribed to the overlapping of the wave func- tions of 2P excited state. It was revealed that the theoretical estimation made through the simplified calculation agreed qualitatively well with the dependence of [g-g]β on [A]. However this calculation presented unsatisfac- tory agreement with the features of [g-g]α and it was suggested that another physical conjecture such as a formation of GaAs-Be alloy should be proposed.

Expanding interest in large-scale fabrication of electronic and photonic devices and in the scale-up of epitoxial growth reactors is creating the need for high quality large diameter InP substrate material. This paper will discuss the evaluating of three-inch diameter semi-insulating Fe-doped InP substrate material purchased from two commercial suppliers. The results of Photon Back Scatter, Infrared Transmission Microscopy, Hall Effect, and Spatially Resolved Photoluminescence measurements will be presented and evaluated.