Fabrication and characterization of native non-polar GaN substrates
Thick c-plane (0001)-oriented native GaN boules that have been produced by hydride vapor phase epitaxy and non-polar native m-plane (1 (1) under bar 0 0) and a-plane (1 1 (2) under bar 0) GaN substrates have been sliced from these crystals using a multivariate saw. An optimized polishing procedure was used to achieve a smooth epi-ready surface morphology on the finished substrates, with an RMS roughness of 0.43 nm. The non-polar Substrates had two types of structural characteristics in appearance : one group was uniform, transparent and nearly colorless: while the second group had regions of varying coloration resulting from transecting V-shape pitting defects in the bulk GaN crystal. These regions had different cathodoluminescence properties but similar dislocation densities of <10(6) cm(-2). The native non-polar GaN substrates had orders of magnitude lower defect densities, including stacking faults, in comparison to heteroepitaxially grown quasi-substrates in non-polar direction on foreign substrates and subsequently delaminated. The Structural characteristics demonstrated the current state-of-the-art in non-polar GaN substrate quality and additionally point at remaining improvement opportunities in substrate size and uniformity. (c) 2008 Elsevier B.V. All rights reserved.
Hanser, D., Liu, L., Preble, E. A., Udwary, K., Paskova, T., & Evans, K. R. (2008). Fabrication and characterization of native non-polar GaN substrates. Journal of Crystal Growth, 310(17), 3953-3956. DOI: 10.1016/j.jcrysgro.2008.06.029