Thermally stable radio frequency power and noise behaviors of AlGaN/GaN high electron mobility transistor without voltage-blocking buffer layer design

The radio frequency (RF) power and noise temperature dependency of buffer-free layer AlGaN/GaN on the 6 in. SiC substrate high electron mobility transistor were studied. The buffer-free structure has improved 3% characteristics of the current collapse and pulse measurement at a 30 V drain quiescent voltage. Compared with the conventional thick buffer layer (1.5-2 μm) structure design, the buffer-free layer with high structural quality AlN nucleation layers can reduce self-heating and thermal boundary resistance effect when the devices operate at a high DC power. The buffer-free device exhibits lower surface temperatures and higher powers at the same V_GS and V_DS than the standard device in thermal imaging measurements. In addition, traditional iron- or carbon-doped buffers were avoided in this design; thus, the buffer-induced microwave noise and thermal noise can be improved simultaneously. Without Fe- or C-doped buffer-induced trap behavior, the buffer-free structure improves the device DC characteristics and reduces the current collapse effect from the conventional buffer; thus, the device shows better linearity, noise figure, and RF small-signal characteristics.