ABSTRACT
There is a growing interest in the application of GaN-based group-III nitrides to the highpower light emitters for indoor and outdoor lightings and the traffic signals. Application to high-power switching is also promising for their high-breakdown field. In order to achieve such high-power devices, in addition to lattice-matching, electrically and thermally conductive substrate is eagerly demanded. Sapphire or SiC are usually used as the substrates for group-IIInitride devices, both of which have a large lattice mismatch against GaN. Moreover, sapphire is electrically insulating and its thermal conductivity is smaller than that of GaN.
