ROOM-TEMPERATURE STABILITY OF THE ELECTRICAL-PROPERTIES OF METALORGANIC VAPOR-PHASE EPITAXIAL HG1-XCDXTE ON GAAS

Significant changes have been observed in the electrical properties after prolonged storage at room temperature of undoped metalorganic vapor phase epitaxial layers of Hg(1-x)Cd(x)Te grown on (100) GaAs. These changes occur in uniform n-type and nonuniform n-p layer structures and are due to the out-diffusion of donors from the bulk of the layers. In situ growth of a surface passivation layer of CdTe prevents these effects and produces stable electrical properties. Uniform n-type layers grown simultaneously on (111) GaAs do not show changes in electrical properties even when not in situ passivated with CdTe. The time dependent properties do not appear to be associated with impurities and are attributed to the diffusion of a combination of native donor defects and Hg acceptor vacancies, which are estimated to have diffusion coefficients, respectively, of 7 x 10(-14) and 2-3 x 10(-16) cm2 s-1 at room temperature.