Analysis of Doping Anomalies in GaAs by Means of a Silicon-Oxygen Complex Model

A model based on the formation of silicon-oxygen pairs is proposed to explain a variety of anomalous phenomena associated with GaAs grown in the presence of silicon, SiO2, and/or oxygen. It is suggested that silicon atoms on gallium sites pair with interstitial oxygen atoms, forming a complex which behaves as an acceptor with energy levels near 0.2 and 0.4 eV below the conduction band. It is assumed that the complex can dissociate upon annealing below 850°C by the reaction 2(SiGaOi)−=(SiGaO2)0+SiGa++3e−. This reaction may be reversed at higher temperatures. The electrical and thermochemical properties of such a complex can explain annealing behavior, the occurence of a mobility maximum between 150 and 200°K, site distribution of silicon in p-type silicon-doped GaAs, change from n- to p-type conductivity as a function of Si concentration in GaAs grown from Ga solutions, the formation of I (insulating) layers in GaAs grown by vapor-phase epitaxy, and some of the anomalous behavior observed in GaAs devices. A variety of growth experiments and characterization techniques which could aid in verification of the SiGaOi complex model are suggested.