ELECTRON-CYCLOTRON-RESONANCE PLASMA PREPARATION OF CDZNTE (211)B SURFACES FOR HGCDTE MOLECULAR-BEAM EPITAXY

CdZnTe wafers were inserted into a multi-chamber processing facility w ithout prior preparation, cleaned by exposure to an electron cyclotron resonance Ar/H-2 plasma, and used as substrates for molecular beam ep itaxy of HgCdTe. Changes induced in the wafer near-surface region duri ng the cleaning step were monitored using in situ spectroscopic ellips ometry. Ellipsometric data were subsequently modeled to provide the ti me evolution of the thickness of a native overlayer. Auger electron sp ectra were consistent with surfaces free of residual contamination and which had the stoichiometry of the underlying bulk. Surface roughness values of 0.4 nm were obtained ex situ using interferometric microsco py. Electron diffraction patterns of plasma prepared wafers heated to 185 degrees C (the temperature required for HgCdTe molecular beam epit axy) were streaked. Structural and electrical characteristics of epila yers grown on these substrates were found to be comparable to those de posited on wafers prepared using a conventional wet chemical process. This demonstrates an important step in an all-vacuum approach to HgCdT e detector fabrication.