Advanced techniques for the magnetotransport characterization of semiconductor IR detector materials are reviewed. Both conventional mixed-conduction and 'mobility spectrum' analyses of the resistivity tensor as a function of magnetic field and temperature are discussed, as well as a hybrid approach which exploits the advantages of both methods. Assuming that the data are sufficiently sensitive, one obtains concentrations and mobilities for each electron and hole species present in a given sample. This is particularly valuable for narrow-gap infrared detector materials such as Hg,,Cd,Te, since the coexistence of multiple species tends to be the rule rather than the exception, and 'anomalous' Hall data are easily misinterpreted if inferences are drawn from measurements at only a single magnetic field. In addition to bulk electron and hole densities and mobilities, one can determine inversion and accumulation layer properties from the anomalous Hall effect, acceptor binding energies and compensation ratios from the low-temperature freeze-out of free holes, and energy gaps from the temperature dependence of the intrinsic carrier concentration. Shubnikov-de Haas and quantum Hall measurements provide additional information about the spatial distribution of the carriers. Electron and hole mobilities in Hg,,Cd,Te detector materials will be briefly reviewed, and theoretical and experimental results compared

Photoluminescence (PL) experiments were carried out at 300 and 12 K to investigate the electro-optical properties of Cd1−xZnxTe grown by molecular beam epitaxy on GaAs substrates. The compositional dependence of the band-gap energy was determined. It has a quadratic dependence on x. The near band edge PL spectra at 12 K show free and bound exciton lines for x=0 and 1 and only broadened bound exciton peaks for other compositions. The bound exciton broadenings are quantitatively explained based on the compositional fluctuations of the cations. The PL line shapes give indications of the high quality of the layers.

CdTe is one of the leading materials used in solar photovoltaics. However, the maximum reported CdTe cell efficiencies are considerably lower than the theoretically expected efficiencies for the ∼1.48 eV CdTe band gap. We report a class of single crystal CdTe-based solar cells grown epitaxially on crystalline Si that show promise for enhancing the efficiency and greatly lowering the cost per watt of single-junction and multijunction solar cells. The current-voltage results for our CdZnTe on Si solar cells show open-circuit voltages significantly higher than previously reported for any II-VI cells and as close to the thermodynamic limit as the best III-V-based cells.

We report the growth and characterization of crystalline, single-phase zinc blende MnS (i.e., β-MnS). The material was grown on ZnSe buffer layers on (100) GaAs substrates, using solid-source molecular beam epitaxy and a novel valved S cracker with deposition at low (∼110 °C) substrate temperatures. Characterization by reflection high energy electron diffraction, high resolution transmission electron microscopy, and low temperature photoluminescence confirms the pseudomorphic nature of the growth. Beyond a certain critical thickness, the layers either become amorphous or convert into the equilibrium rock salt polymorph (α-MnS), depending on the growth temperature.

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