Mg segregation in a (1(1)over-bar01) GaN grown on a 7° off-axis (001) Si substrate by MOVPE

Redistribution behavior of magnesium (Mg) in the N-terminated (1 (1) over bar 01) gallium nitride (GaN) has been investigated. A nominally undoped GaN layer was grown on a heavily Mg-doped GaN template by metalorganic vapor-phase epitaxy (MOVPE). Mg dopant profiles were measured by secondary ion mass spectrometry (SIMS) analysis. A slow decay of the Mg concentration was observed in the nominally uncloped GaN layer due to the surface segregation. The calculated decay lengths of the (1 (1) over bar 01) GaN are similar to 75-85 nm/decade. These values are shorter than the decay length determined in the sample grown on the Ga-terminated (0001) GaN. This result indicates that Mg exhibited weak surface segregation in the (1 (1) over bar 01) GaN as compared to the (0001) GaN. The weak surface segregation is in agreement with the high efficiency of Mg incorporation on the (1 (1) over bar 01) face. The high density of hydrogen was obtained in the (1 (1) over bar 01) GaN, which might enhance the Mg incorporation. (C) 2009 Elsevier B.V. All rights reserved.