Gate I-V characteristics degradation in AlGaN/AlN/GaN HEMTs

AlGaN/AlN/GaN high electron mobility transistor (HEMT) is one of the most promising device structures for high frequency power applications. Although high power density was demonstrated by number of groups [1], several unresolved issues remain. One of them is the gate breakdown under forward bias. Figure 1 shows the typical gate I-V characteristics of the devices obtained by applying voltage (V_g) between gate and drain with source floating. At certain voltage (4.5-6 V), the gate current (I_g) increases instantaneously. The change is permanent with current in both forward and reverse direction increased by several orders of magnitude.