Molecular-beam epitaxy growth of dilute GaAsN alloys by surface nitridation

This paper presents the growth of GaAsN pseudo-alloys by a surface nitridation method that consisted of a repeated cycle of nitridation of the GaAs (001) surface, growth interruption and growth of a GaAs overlayer. Surface reconstruction during the nitridation process changed from (2×4) to (1×4) and (3×4) phases above 540 °C with the increase of nitridation time, resulting in a higher N compositions of the alloys. It was revealed that an excessive nitridation resulted in the degradation of the photoluminescence (PL) intensity. While the N composition slightly decreased with the interruption time, less impact appeared on their crystallinity characterized by PL measurement. As a result, the N composition was controllable between 1% and 5% by the combination of growth temperatures (460-600 °C) and thicknesses of the GaAs overlayer (2-8 monolayers; MLs). The thickness of the GaAs overlayer should be designed over 4 ML to form a flat surface for the next nitridation process. The integrated PL intensity of GaAs0.97N0.03 alloys was increased by 7 times compared to the one grown by conventional growth method (continuous supply), indicating the improved crystalline quality of the GaAsN alloys.