N-face GaN() films grown by group-III-source flow-rate modulation epitaxy

Abstract

N-face GaN() films were grown on sapphire substrates with a very small misorientation angle (0.15°) by flow-rate modulation epitaxy (FME). We investigated two types of FME: FME in which Ga precursor with flow rate of 2.08 × 10−5 mol/min is intermittently supplied (intermittent supply of group-III-source FME) and in which Ga precursors with flow rates of 2.08 × 10−5 and 1.04 × 10−5 mol/min are alternately supplied (group-III-source FME). Etching of GaN films is effectively suppressed in group-III-source FME, while the etching significantly impedes the growth rate in intermittent supply of group-III-source FME. Group-III-source FME promotes surface migration of Ga adatoms, thus terminating the formation of hillocks on N-face GaN() surfaces.