Higher Dislocation Density of Arsenic-Doped HgCdTe Material

There is a well-known direct negative correlation between dislocation density and optoelectronic device performance. Reduction in detector noise associated with dislocations is an important target for improvement of mercury cadmium telluride (Hg 1− x Cd x Te)-based material in order to broaden its use in the very long-wavelength infrared (VLWIR) regime. The lattice mismatch and differences in physical properties between substrates and the epitaxial Hg 1− x Cd x Te layers cause an increased threading dislocation density. As demonstrated in this work, the presence of arsenic impurities via p -type doping in molecular beam epitaxy (MBE)-grown epitaxial crystal structure increases the etch pit density (EPD) of Hg 1− x Cd x Te grown on Si substrates but not on CdZnTe substrates. This EPD increase is not observed in indium n -type-doped Hg 1− x Cd x Te grown on either Si or CdZnTe substrates. This trend is also seen in layers with different cadmium compositions. All of the EPD variations of the structures studied here are shown to be independent of the MBE machine used to grow the structure. The fundamentals of this higher EPD are not yet completely understood.