Defect reduction in non-polar (11-20) GaN grown on (1-102) sapphire
Johnston, C F and Kappers, M J and Moram, M A and Hollander, J L and Humphreys, C J
This work assesses the relative effectiveness of different techniques to reduce defect density in heteroepitaxial, non-polar, a -plane GaN films grown on r -plane sapphire by MOVPE. Plan view TEM was used to obtain the defect density of films grown by different methods. The as-grown material was found to have a high dislocation and basal plane stacking fault (BSF) density (1.9 (± 0.2) × 10\^11 cm–2 and 1.1 (± 0.9) × 10\^6 cm–1 respectively). The four defect reduction techniques tested were: 3D–2D growth, SiNx interlayers, ScN interlayers and epitaxial lateral overgrowth (ELOG). Both dislocation and BSF density were reduced by all methods compared to the as-grown material. The lowest defect density was achieved in the (0001) wing of the ELOG sample and was <1 × 10\^6 dislocations cm–2 and 2.0 (± 0.7) × 10\^4 BSFs cm–1. On the wafer scale, ScN interlayers were most effective: A single 5 nm thick ScN interlayer reduced the BSF density to 5.9 (± 0.8) × 10\^5 cm–1 and the dislocation density was reduced by two orders of magnitude to 1.8 (± 0.2) × 10\^9 cm–2 compared to the as-grown material.
Department of Materials
Imperial College London
Royal School of Mines
London, SW7 2AZ - UK