Effect of isovalent doping with phosphorus on the cluster formation in gallium arsenide grown by molecular-beam epitaxy at a relatively low temperature

Transmitting electron microscopy and X-ray diffractometry are used to study the GaAs layers undoped or doped uniformly with phosphorus (2.3 mol %) and grown at a temperature of 250°C and then annealed isochronously at 400, 500, 600, or 700°C. It is ascertained that doping with phosphorus reduces the amount of excess arsenic captured in the layer in the course of growth and also brings about a retardation of precipitation during subsequent annealing. The concentration of excess arsenic in undoped samples amounted to ∼0.2 at %; clusters were observed after annealing at a temperature of 500°C. The concentration of excess arsenic amounted to 0.1 at % in the samples containing phosphorus; in this case, the clusters were observed only after a heat treatment at 600°C. The average size of clusters in doped samples is smaller than that in undoped samples at the same heat-treatment temperatures.