We studied the effect of in situ etching and cleaning on air-exposed regrown interfaces for p/n-type GaAs and Al0.5Ga0.5As layers. The layers were grown by MOCVD and etched using HCl gas or HCl with the addition of group III, group V, and group III+ V gases. Silicon is the dopant for the n-type samples. In addition, silicon is one of the impurities present in HCl gas, and is seen accumulated at the interfaces in this study. This interfacial silicon leads to significant carrier variation at the regrown interfaces within the GaAs samples. Oxygen is also a primary impurity at regrown interfaces, which can be removed through the introduction of AsH3 for GaAs. In the Al0.5Ga0.5As samples, other impurities were found at these interfaces including a high concentration of oxygen with lesser concentrations of Si, H, C, Cl, and Zn (only for the p-type). AsH3 introduction did not effect a reduction in impurities at the Al0.5Ga0.5As regrown interface. The different behaviors of Al0.5Ga0.5As and GaAs regrown interfaces were also studied using density functional theory to identify various oxygen removal pathways for the various chemistries employed in this study. (C) 2004 Elsevier B.V. All rights reserved.