Reduction in residual impurities in semi-polar 303¯1¯ and 202¯1¯ GaN grown by metalorganic vapor phase epitaxy

Abstract We report on residual impurities in semi-polar 3 0 3 ¯ 1 ¯ and 2 0 2 ¯ 1 ¯ GaN homo-epitaxial layer grown by metal-organic chemical vapor deposition. The 3 0 3 ¯ 1 ¯ and 2 0 2 ¯ 1 ¯ GaN layer showed atomically smooth surface and clear steps toward 1 0 1 ¯ 6 and 1 0 1 ¯ 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 2 0 2 ¯ 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 3 0 3 ¯ 1 ¯ and 2 0 2 ¯ 1 ¯ GaN epitaxial layers are promising candidates in obtaining a high quality GaN drift layer for vertical GaN devices.