Regrowth of high-quality Al0.3Ga0.7As/GaAs superlattices on laterally oxidized digital AlxGa1−xAs (x>0.80) alloys

Abstract

Digital AlxGa1−xAs 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 AlxGa1−xAs (x>0.8) alloys were determined. Decreasing aluminum compositions resulted in slower oxidation rates, similar to true AlxGa1−xAs alloys. Further investigations of the oxidation characteristics of a digital Al0.98Ga0.02As 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 Al0.3Ga0.7As/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 AlxGa1−xAs alloys for regrowth applications.