AlGaN/GaN HEMTs grown by MBE on semi-insulating HVPE GaN templates

Summary form only given. Attempts to circumvent the low thermal conductivity of sapphire substrates by including in a device structure a thick (15 μm) GaN buffer grown by HVPE between the sapphire substrate and the MBE device layer stack. The heat generated in the device close to the surface of the structure is spread laterally in the HVPE buffer, increasing the effective thermal area of the device, and lowering the thermal impedance of the HEMT device. In contrast to SiC, the sapphire substrate technology is mature and affordable. Principally, both MBE and HVPE growth may be scaled up in area to grow on readily available large diameter sapphire substrates.