Photoluminescence study of acceptors in silicon-doped gallium arsenide grown by metalorganic chemical vapor deposition

Abstract

Epitaxial silicon-doped GaAs layers were grown by metalorganic vapor deposition (MOCVD) using a silane-argon mixture as a dopant source. Two different dopant sources with silane mole fractions 2.4×10 −4 and 2.3×10 −5 were used. For both sources the electron concentration increased with the silane mole fraction in the gas flow, reached a maximum, and then fell abruptly. The maximum electron concentration was substantially higher (up to 2.1×10 19 cm −3) for layers grown with a more concentrated dopant source. The difference in silicon incorporation from different silane sources is thought to be caused by uncontrollable impurities in the diluting gas - argon. The low temperature (12 and 80 K) photoluminscence investigation revealed the presence of at least three types of acceptors in the layers: residual impurity zinc, group IV acceptors silicon versus carbon and the deep acceptor complex, silicon donor-gallium vacancy, responsible for the emission band with peak energy 1.24 eV. As a rule, this emission band was dominant in the most heavily doped layers with low electron mobilities, and its intensity was low for layers with good mobility values. Therefore the silicon donor-gallium vacancy complex is thought to be the main compensating acceptor in most heavily doped layers.