Growth of highly resistive Ga‐polar GaN by LP‐MOVPE

Abstract

Electrical characteristics of 1.3 µm thick GaN films were investigated with respect to the polar type. Unintentionally doped N-polar GaN grown on nitrided sapphire substrates had a hexagonal facetted morphology and consistently exhibited a high n-type conductivity with a sheet resistance of ∼10 Ω/sq, corresponding to a carrier concentration on the order of 1019 cm–3. In contrast, Ga-polar GaN films grown on low temperature AlN buffer layers showed a high sheet resistance of ∼109 Ω/sq. GaN films of mixed polarity exhibited sheet resistance in-between the two extreme values obtained for polarity pure films. The results of this work show that the existence of N-polar domains (even on the nano-scale) in an otherwise Ga-polar matrix significantly decreases the insulating properties of unintentionally doped GaN films. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)