Abstract
AbstractHigh‐quality GaN substrates with a thickness of 0.5 to 1.2 mm were prepared by halide vapor‐phase epitaxy (HVPE) on c‐plane sapphire and by means of a post‐growth laser‐induced lift‐off or natural stress‐induced (self‐) separation process. Structural, optical and electrical properties of the grown material were studied in detail. Resistivity and doping concentrations dependence on temperature were investigated and the results revealed a low donor concentration (2 × 1015 cm‐3 at 273 K) and a moderate resistivity (10‐48 Ωcm) of the samples. Several deep levels observed in the DLTS spectra were identified. The study shows that the GaN material is self‐compensated and a strong influence of point defects related to dislocations on electronic transport is observed. The HVPE growth on InGaN/GaN multi‐quantum wells buffer layers and subsequent self‐separation method was seen as advantageous, in comparison to the laser‐induced lift‐off one, in respect to a lower cost and better crystalline quality of the GaN material obtained (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
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