Correlation between the leakage current and the thickness of GaN‐layer of AlGaN/GaN‐HFET

For further improvements in AlGaN/GaN heterojunction field-effect transistor performance, it is necessary to reduce the buffer leakage current of the GaN layer. We studied the correlation between the buffer leakage current and the thickness of GaN layers. Unintentionally doped GaN layers with different thicknesses from 0.2 μm to 2 μm were grown by metal organic chemical vapor deposition on SiC substrates. The buffer leakage current of the GaN layer was measured after deposition of ohmic metal contact and the dislocations were observed using a transmission electron microscopy. The thinner samples had a smaller buffer leakage current although a higher density of threading dislocations. We discussed the origin for the reduction in the buffer leakage current for the thinner GaN layers by assuming that the residual carrier in the GaN layer was compensated by dislocations. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)