Microstructural characterization of low-temperature grown GaMnN on GaAs(0 0 1) substrates by plasma-assisted MBE

Abstract

GaMnN layers have been grown on GaAs(0 0 1) substrates by plasma-assisted molecular beam epitaxy (PAMBE), under both N-rich and Ga-rich conditions, at temperatures from 680 °C down to 186 °C. Under N-rich conditions, a reduction in the growth temperature results in a transition from faulted single-crystalline zinc-blende layer growth to mixed-phase zinc-blende and wurtzite polycrystalline layer growth, whilst being also associated with increasing levels of Mn incorporation. Improved layer crystallinities were associated with PAMBE growth under Ga-rich conditions. In particular, a tilted, mixed-phase growth mode allowing for the deposition of comparably uniform GaMnN alloys, at a level of ∼3.5 at% Mn, was identified for slightly Ga-rich conditions at a reduced temperature of ∼265 °C. No correlation could be established between the GaMnN/GaAs (0 0 1) fine-scale defect structures and the layer functional properties, with all the free-standing layers showing p-type conductivities and comparable mobilities.