AlGaN-GaN HEMTs and HBTs for microwave power

Summary form only given. The AlGaN-GaN based material system offers the three most important materials properties required for efficient microwave power generation: very high breakdown electric field (/spl sim/2 MV/cm), high electron mobility and velocity (/spl mu//sub c//spl sim/1000 cm/sup 2//spl middot/V/sup -1/s/sup -1/ and v/sub s//spl sim/2/spl times/10/sup 7/ cm/spl middot/s/sup -1/ in bulk materials) and heterojunction technology to optimize device design. This has led to the rapid development of AlGaN-GaN HEMTs, grown heteroepitaxially on either sapphire or SiC substrates. AlGaN-GaN HBTs also show promise for power amplifier and switching applications. Inherent strengths of the HBT structure include high current densities and low phase noise, as well as improved linearity and threshold control. The progress in HEMT DC and RF performance has been spectacular and the possibility of insertion into high power systems is a distinct possibility. The HBTs continue to have to battle problems with p-type doping and associated processing difficulties. However, sustained progress in engineering around this problem holds promise for the future.