Temperature stability of AlxGa1−xAs (0≤x≤1) thermal oxide masks for selective-area epitaxy

Abstract
The use of thermal oxides of AlxGa1−xAs (0≤x≤1) as masking materials for selective‐area epitaxy by organometallic chemical‐vapor deposition has been investigated. It was found that the thermal oxide of GaAs is only applicable for low growth temperatures (≤600 °C), and the addition of aluminum significantly improves the thermal stability of the oxide. The oxide of Al0.4Ga0.6As is suitable for high‐temperature deposition, but there are criteria for the thickness and oxidation temperature. Thin layers of AlAs oxidized at 475 °C are excellent masks and allow precise thickness control. Promising results of selective‐area deposition using these aluminum oxide masks have been obtained. High‐quality single crystal grew in mask openings uniformly surrounded by dense and fine‐grain polycrystalline deposits, producing a planar duplication of the original pattern.