The effect of the initial growth conditions, and lattice matching, upon the deep-level spectrum of n-type ZnSe, grown onto GaAs by means of molecular-beam epitaxy, was investigated using deep-level optical spectroscopy. A detailed study of the steady-state and transient photocapacitances permitted the measurement of the optical threshold energies, concentrations and emission rates of electronically active defects in the ZnSe layer. Several deep levels were found, at Ec - Et = 1.15, 1.46, 1.90 and 2.25eV; with concentrations in the range of 1012 to 1014/cm3. When a 2nm-thick composition-controlled interface layer was grown using various beam pressure ratios, prior to ZnSe growth, a distinct decrease in the 1.46eV level concentration occurred with increasing Se content. The deposition of a lattice-matched InGaAs buffer layer, prior to ZnSe growth, reduced the concentrations of both the 1.15 and 1.46eV levels by more than an order of magnitude. Depth profiling of defect distributions within the ZnSe overlayer was also performed. It was found that only the concentration of the 2.25eV level exhibited a dependence upon depth. This increased as the II-VI/III-V interface was approached.

Photocapacitance Study of Bulk Deep Levels in ZnSe Grown by Molecular-Beam Epitaxy A.Hierro, D.Kwon, S.A.Ringel, S.Rubini, E.Pelucchi, A.Franciosi: Journal of Applied Physics, 2000, 87[2], 730-8