Scanning Tunneling Microscopy Study of Cr-doped GaN Surface Grown by RF Plasma Molecular Beam Epitaxy

摘要

Cr doped GaN was grown by rf N-plasma molecular beam epitaxy on sapphire (0001) at a sample temperature of 700 °C. Cr/Ga flux ratio was set to a value from 5% to 20%. Subsequently, scanning tunneling microscopy was performed on these surfaces. Cr incorporates on the GaN surface at 700 °C at a Cr concentration of 5% and less. By increasing the Cr/Ga flux ratio to 20% in CrGaN, linear nano structures were formed on the surface, which were not observed on the bare GaN surface. The RHEED and STM studies reveal that Cr atoms form 3x3 reconstruction when 0.1 ML of Cr was deposited at room temperature on 1 x 1 adlayer of Ga on GaN (000-1). Cr substitutes Ga on the surface when deposited at 700 °C on the MBE grown GaN (000-1) surface fur all the experiments, which we have performed, provided the Cr concentration is low (～5%).