THERMAL MODELLING OF MULTI - FINGER ALGAN / GAN HEMT ’ s

AlGaN/GaN high electron mobility transistors (HEMTs) are very promising for high power applications at microwave frequencies. The heterostructures are usually grown on SiC or sapphire substrates. Sapphire substrates are relatively cheap, but their low thermal conductivity is a major disadvantage. To improve the thermal performance, a hybrid integration of the HEMT onto an AlN carrier substrate is proposed. In this study we compare two different hybrid integration schemes for multi-finger HEMTs: a flip-chip integration and an integration where the sapphire substrate is removed by laser lift-off. The two structured are compared using finite element analysis. After experimental validation of the modelling, both structures are thermally optimized.