Effect of arsenic dimer species to silicon doping of GaAs layers prepared by molecular beam epitaxy

Abstract

A strong dependence of Si doping on dimer arsenic (As2) flux and substrate temperature is observed for GaAs films grown by molecular beam epitaxy. Using an arsenic effusion cell with a cracker, Si doping levels are shown to depend on the cracking efficiency and substrate temperature. With the same Si cell temperature and GaAs growth conditions, the measured carrier concentration of the grown films decreases as the cracker temperature (cracker current) is increased and this dependence becomes stronger as the substrate temperature is increased. For samples grown at 660 °C, more than a factor of four decrease of the doping concentration is observed for the cracker current changing from 5 to 6.5 A. For those grown at 560 °C, there is only a weak dependence. Evidence is given to show that carbon contamination and Si self-compensation are not the causes of this effect. The formation of volatile SixAsy compound at the substrate surface is proposed to account for this phenomenon.