CHARACTERIZATION OF EPITAXIAL ZNSE GAAS(100) INTERFACE PROPERTIES ANDTHEIR CONTROL BY (HF+SE)-PRETREATMENT/

Interface properties of molecular beam epitaxy (MBE)-ZnSe/GaAs (100) s ubstrate systems formed after various pretreatments of the substrate s urface, including standard chemical etching, and (NH4)(2)S-x-, HF-, Te -, Se- and (HF+Se)-pretreatments, have been characterized by C-V, deep level transient spectroscopy (DLTS) and I-V measurements. A comparati ve study of the quality of the grown epilayer has also been made by X- ray diffraction (XRD) and Raman scattering measurements. It is found t hat the (HF+Se)-pretreatment gives superior interface with minimum int erface state density, N-ss,N-min, which is smaller than 1x10(11) cm(-2 ) eV(-3) below the midgap of GaAs. The value is about a thirtieth of t he standard chemically etched sample. The influence of interface state s on I-V characteristics across the interface is also analyzed on the basis of a model which takes interface charge into consideration. The excess voltage drop at the interface is considerably reduced for the S e-pretreated sample, which is in agreement with the present model. The quality of the ZnSe epilayers assessed by XRD and Raman spectra is fi rmly correlated with the interface quality.