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

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)