Microstructure and wet oxidation of low-temperature-grown amorphous (Al/Ga,As)

Amorphous and polycrystalline compounds of (Ga,As) and (Al,As) grown at ver y low temperatures by molecular-beam epitaxy are characterized. The ultimat e microstructure and the amount of excess arsenic incorporated in the (Ga,A s) or (Al,As) layers are found to depend on the arsenic overpressure during the low-temperature growth. With lower arsenic overpressure, a polycrystal line structure prevails and less excess arsenic is observed inside the laye r. In contrast, a high incorporation of excess arsenic achieved by high-ars enic overpressures leads to the formation of amorphous films. Upon wet oxid ation, the lateral oxidation rate of (Al,As) is found to depend on the crys tallinity of the (Al,As) layer and the amount of excess arsenic. During the same process, recrystallization proceeds in the (Ga,As) layer. (C) 2001 Am erican Institute of Physics.