Structural and Photoluminescence Characterization of CdS/GaAs Films and CdS-ZnS Strained-Layer Superlattices Grown by Low-Pressure MOCVD Method

Abstract

Single-crystalline CdS films have been epitaxially grown on (100) and (111)A and B GaAs substrates at temperatures between 200 and 350°C by a low-pressure metalorganic chemical-vapor-deposition (MOCVD) method using (CH₃)₂Cd and H₂S gases. The (100)-oriented film exhibits perfectly cubic modification, but contains dislocations and stacking faults. Moreover, the films on (111)A and B substrates show pure hexagonal growth. In particular, the photoluminescence (PL) spectrum at 4.2 K of the film grown on the (111)A substrate is characteristic of a hexagonal wurtzite crystal and is dominated by the presence of the strong I ₂ (neutral-donor bound exciton) line at 2.547 eV and I ₁ (neutral-acceptor bound exciton) line at 2.534 eV, and a donor-acceptor pair (I _E) band at 2.447 eV. CdS-ZnS strained-layer superlattice has for the first time been fabricated on GaAs substrate by MOCVD. The structural and 4.2 K PL properties are also presented.