Si incorporation in Al_xGa_1−xAs grown by molecular beam epitaxy

The incorporation of Si in Al_0.25Ga_0.75As was studied as a function of Si cell temperature and substrate growth temperature. Within experimental error, the measured electron concentration was equal to the Si atomic concentration as determined by secondary ion mass spectroscopy. For substrate growth temperatures much above 650 °C, the Si concentration decreased with increasing substrate temperature. This is attributed to a possible decrease in the effective group V/III ratio and evaporation of Si. For Si cell temperatures above 1150 °C, stacking faults in the surface morphology indicated the initiation of Si precipitation. Electron mobilities at room temperature were between 1300 and 600 cm²/Vs, decreasing at higher doping levels. The donor activation energy was observed to increase as a function of both Si cell temperature and substrate growth temperature.