NATIVE DEFECT ENGINEERING OF INTERDIFFUSION USING THERMALLY GROWN OXIDES OF GAAS

Interdiffusion can be either increased or decreased when annealing epi taxial layers covered by an oxide of GaAs. AlGaAs/GaAs quantum wells ( QWs) of different widths were grown by organometallic vapor phase epit axy, A top layer of GaAs was thermally oxidized at 450 degrees C, and rapid thermal annealing (RTA) was performed at 950 degrees C under Ar. Photoluminescence showed that an order of magnitude increase in inter diffusion occurred in the oxide-covered QWs compared to uncovered QWs. However, when a thin layer of Al was evaporated over the oxide layer prior to RTA, the rate of interdiffusion was reduced by mon than order of magnitude compared to that of uncovered QWs, Interdiffusion slows because the oxide, composed primarily of Ga2O3, is quickly reduced by Al metal during RTA to form atomic Ga and Al2O3. The Al2O3 layer forme d over the QWs traps the free Ga as interstitials in the GaAs. The exc ess Ga interstitial concentration reduces the group III vacancy concen tration, and it is this reduction in group III vacancy concentration w hich slows the interdiffusion rate. The results show that metallurgica l reactions may be used as a tool for engineering native defect concen trations and associated diffusivities. (C) 1998 American Institute of Physics. [S0003-6951 (98)03332-4].