Study of HgCdSe Material Grown by Molecular Beam Epitaxy

Much progress has been made in developing high-quality HgCdTe/Si for large-area focal-plane array (FPA) applications. However, even with all the material advances made to date, there is no guarantee that this technology will be mature enough to meet the stringent FPA specifications required for long-wavelength infrared (LWIR) systems. With this in mind, the Army Research Laboratory (ARL) has begun investigating HgCdSe material for infrared (IR) applications. Analogous to HgCdTe, HgCdSe is a tunable semiconductor that can detect any wavelength of IR radiation through control of the alloy composition. In addition, several mature, large-area bulk III-V substrates are nearly lattice matched to HgCdSe, giving this system a possible advantage over HgCdTe, for which no scalable, bulk substrate technology exists. We have initiated a study of the growth of HgCdSe using molecular beam epitaxy (MBE). Growth temperature and material flux ratios were varied to ascertain the best growth conditions. Smooth surface morphology has been achieved using a growth temperature much lower than that used for HgCdTe. Additionally, zero void defects were nucleated at these lower temperatures. Preliminary data suggest a linear relationship between the Se/Cd flux ratio used during growth and the cutoff wavelength as measured by Fourier-transform infrared (FTIR) spectroscopy.