Ohmic Contact Properties of Photo-Chemically Etched Nonpolar A-Plane (112¯0) GaN Films

• Published in: ECS journal of solid state science and technology 2017-01, Vol.6 (11), p.S3001-S3004
• Main Authors: Baik, Kwang Hyeon, Lee, Sohyun, Jang, Soohwan
• Format: Article
• Language: English
• ISSN: 2162-8769; 2162-8769; 2162-8777
• DOI: 10.1149/2.0011711jss

Nonpolar a-plane (112¯0) GaN (a-GaN) was photo-chemically etched under ultraviolet illumination using alkali KOH solution, and the Ohmic contact properties on the etched a-GaN epitaxial layer were investigated. After photo-chemical etching, the striated surface morphology along the c-axis [0001] direction was obtained having triangular prisms consisting of m-plane {101¯0} facets. The properties of Ti/Al/Ni/Au Ohmic contact on surface-textured a-GaN films were studied with transmission line method patterns aligned along the specific crystal orientations. The minimum specific contact resistance of 9.97 × 10−5 Ω·cm2 was achieved along the c-axis on the etched GaN surface at the annealing temperature of 750°C. The etched a-GaN showed higher electrical conductivity along the c-axis than along m-axis. This anisotropic behavior is in contrast to that of the unetched a-GaN where carrier scattering by basal plane stacking faults in the direction perpendicular to the c-axis is a major factor in determining opposite anisotropic conductivity. The higher conductivity along the c-axis of the etched a-GaN film could be explained by more dominant effect of surface roughness scattering.