Annealing dynamics of molecular-beam epitaxial GaAs grown at 200°C

By separating a 2-μm-thick molecular-beam-epitaxial GaAs layer grown at 200°C from its 650-μm-thick substrate, we have been able to obtain accurate Hall-effect and conductivity data as functions of annealing temperature from 300 to 600°C. At a measurement temperature of 300 K, analysis confirms that hopping conduction is much stronger than band conduction for all annealing temperatures. However, at higher measurement temperatures (up to 500 K), the band conduction becomes comparable, and a detailed analysis yields the donor and acceptor concentrations and the donor activation energy. Also, an independent absorption study yields the total and charged As concentrations. Comparisons of all of these quantities as a function of annealing temperature T show a new feature of the annealing dynamics, namely, that the dominant acceptor (probably V related) strongly decreases and then increases as T is increased from 350 to 450°C. Above 450°C, N, N, and [As] all decrease, as is known from previous studies.