Reduction in residual impurities in semi-polar [formula omitted] and [formula omitted] GaN grown by metalorganic vapor phase epitaxy

Abstract

We report on residual impurities in semi-polar 303¯1¯ and 202¯1¯ GaN homo-epitaxial layer grown by metal-organic chemical vapor deposition. The 303¯1¯ and 202¯1¯ GaN layer showed atomically smooth surface and clear steps toward 101¯6 and 101¯4, respectively. The residual impurity concentrations of oxygen and carbon were below the detection limit of secondary-ion mass spectroscopy. Low-temperature photoluminescence revealed that 202¯1¯ GaN layer consisted free excitons and Si donor bound excitons, along with two-electron satellite lines and longitudinal optical (LO) phonon coupling transitions. The results indicate semi-polar 303¯1¯ and 202¯1¯ GaN epitaxial layers are promising candidates in obtaining a high quality GaN drift layer for vertical GaN devices.