language: en

[Confidential: not for distribution. Submitted to IOP Publishing for peer review]

12 December 2009

Measuring dislocation densities in nonpolar a-plane GaN films using atomic force microscopy

by M. A. Moram a) , C. F. Johnston, M. J. Kappers, C. J. Humphreys
Dept. Materials Science & Metallurgy, University of Cambridge,
Pembroke St., Cambridge, CB2 3QZ, UK

Dislocation densities in nonpolar GaN films were determined using microscopy (AFM) by counting pits in the GaN surface revealed by a SiH 4 surface treatment. This treatment increased the number of pits detected by a factor of 2 compared to the untreated surface. AFM and transmission electron microscopy analysis of a series of SiH 4 -treated calibration samples indicated that surface pit and dislocation densities corresponded well up to a dislocation density of ~6 x 10 9 cm -2 , above which surface pit overlap meant that dislocation densities determined by AFM were underestimated. For all samples with dislocations densities below 6 x 10 9 cm -2 , spatial analysis of the surface pit positions showed that dislocations typically accumulated in bands at island coalescence boundaries.

Keywords: A1. Atomic force microscopy, A1. Line defects, A1. Planar defects, A3. Metalorganic vapour phase epitaxy, B1. Nitrides, B2. Semiconducting III-V materials PACS codes: 61.72.Ff, 61.72.Lk, 61.72.Nn, 61.72.uj, 68.37.Ps, 81.05.Ea a) Email: mam65@cam.ac.uk, Tel: +44 1223 334375