Effect of Schottky Barrier Characteristics on the Power Density and Stability of GaN HFETs

GaN heterojunction field-effect transistors (HFETs) were fabricated by the standard process on SiC substrates. The forward characteristics were measured and the ideality factor n is calculated. The power performances of packaged devices have been got by the microwave power measure system for long time tests. The results show that the high power stability characteristics can be obtained by decreasing the n value. The lowest n value was 2.1 and the corresponding 1-mm-wide HFET biased at a drain voltage of 30V demonstrated a continuous wave saturated output power of 6.3W with an associated large-signal gain of 5dB and a power-added efficiency (PAE) of 31.96% at 8GHz, and the power degradation was negligible, about 0.79% in five minutes. When the n value increased to 5, the CW power decreased to 3.6W and the degradation was obvious, about 8.33% in five minutes. The results have demonstrated that decreasing the ideality factor n by optimizing the process can improve the power density and stability greatly