Regrowth of high-quality Al_(0.3)Ga_(0.7)As/GaAs superlattices on laterally oxidized digital Al_(x)Ga_(1-x)As (x0.80) alloys

摘要

Digital Al_(x)Ga_(1-x)As alloys consisting of a repeated structure of alternating layers of AlAs and GaAs were grown between layers of GaAs. Lateral oxidation characteristics of these digital Al_(x)Ga_(1-x)As (x>0.8) alloys were determined. Decreasing aluminum compositions resulted in slower oxidation rates, similar to true Al_(x)Ga_(1-x)As alloys. Further investigations of the oxidation characteristics of a digital Al_(0.98)Ga_(0.02)As alloy indicate that shorter periods (24.5 monolayers (ML) AlAs/0.5 ML GaAs) showed slower oxidation rates than the longer period alloys (49 ML AlAs/1 ML GaAs or 98 ML AlAs/2 ML GaAs). As the GaAs layers become closer together (that is a digital alloy with a shorter period), the material more closely resembles a true alloy showing slower oxidation rates. Regrowth of an Al_(0.3)Ga_(0.7)As/GaAs superlattice on the laterally oxidized samples, capped with a thin GaAs layer, was performed. The high-temperature regrowth process caused delamination problems for the oxidized conventional AlAs material, resulting in a rough surface morphology causing a decrease in photoluminescence (PL) intensity. Oxidized digital alloys allowed for a large increase in useable surface area and higher PL intensities, indicating the superiority of the digital Al_(x)Ga_(1-x)As alloys for regrowth applications.