Influence of the Cap Layer Thickness on the Interface Quality in In0.2Ga0.8As/GaAs Single Quantum Wells

Abstract

We have investigated the influence of the cap layer thickness on the interface quality in MBE grown partially relaxed, 250 Å thick In0.2Ga0.8As/GaAs single quantum wells using 77 K photoluminescence and high resolution X-ray diffraction. By increasing the GaAs cap layer thickness from 50 to 5000 Å, the interface quality was improved from presence of double-kink misfit dislocations (partial relaxation) to a nearly dislocation free situation (full strain). This strain modification with GaAs cap layer thickness was explained by increased line tension and dislocation interactions based on the Matthews and Blakeslee model.