AlGaN/GaN Heterojunction Bipolar Transistors With High Current Gain and Low Specific on-Resistance

AlGaN/GaN heterojunction bipolar transistors with low dynamic RON,sp and Vth hysteresis

“…At OFF-state collector bias V CEQ = 80 V, the device shows a low dynamic specific on-resistance (R ON,sp ) of 0.316 mΩ•cm 2 , which is only 4.7% higher than static R ON,sp , thanks to current conductive path far from the surface. A threshold voltage (V th ) of 3.58 V extracted at 1 A/cm 2 is achieved with an on/off current ratio of 2×10 7 . The device also shows a large base voltage swing of -7 to 7 V with a small V th hysteresis of 50 mV.…”

“…Sub-micrometer fin channels in Fin-JFETs help to achieve superior gate control and normally-off operation. On the other hand, GaN heterojunction bipolar transistors (HBTs) have also been proposed as power switching devices [5][6][7][8], which are also vertical structures, with the advantages of low photolithography accuracy, normally-off operations, high current density, strong avalanche breakdown ability and lower RON,sp due to conductivity modulation effect. Up to date, some promising results have been reported of GaN HBTs, such as high electric field near to 3 MV/cm [7][8][9] and high current density (141 kA/cm 2 on GaN-on-GaN HBT [10]).…”

“…The device shows a low dynamic R ON,sp of 0.316 mΩ•cm 2 at OFF-state collector bias (V CEQ ) of 80 V, which only degrades by 4.7% compared with the static R ON,sp . A threshold voltage (V th ) of 3.58 V defined at 1 A/cm 2 is achieved with an on/off current ratio of 2×10 7 . The device also shows a large base voltage swing of ±7 V with a small V th hysteresis of 50 mV.…”

“…The schematic of the device is shown in Figure 1. Detailed epitaxial growth techniques and device preparation processes were reported in the previous work [7,13]. The emitter size is 5 (W E )×10 (L E ) μm 2 , and the emitter metal width is 2 μm.…”

“…Fully vertical GaN-on GaN HBTs can avoid surface traps and reduce the defects in the collector, which is expected to further reduce current collapse. Figure 3 (a) shows the transfer characteristics of the HBT at V CE of 3 V. A V th of 3.58 V is measured at 1 A/cm 2 with an on/off ratio over 2×10 7 . The V th hysteresis is low to 50 mV between the up-and down-sweep of V B from −7 to 7 V. This value is relatively low compared with GaN HEMTs, owing to almost eliminated surface state trapping [12,16].…”