GaN/InGaN heterojunction bipolar transistors with ultra‐high d.c. power density (>3 MW/cm²)

Abstract

We report ultra-high-power performance on npn GaN/InGaN double heterojunction bipolar transistors (DHBTs) that is directly grown on a free-standing (FS) GaN substrate. Measured common-emitter current gain (h fe ) reaches 80. A quasi-static I-V measurement shows that J C > 141 kA/cm 2 and a power density of 3.05 MW/cm 2 can be achieved for DHBTs grown on an FS-GaN substrate. When the temperature is increased to 250 8C, a GaN/InGaN DHBT shows h fe ¼ 43 and the offset voltage is reduced from 0.8 V at the room temperature to 0.3 V. Similarly, the knee voltage is reduced from 5.2 V at room temperature to 2.75 V at 250 8C. In this particular device, breakdown voltage (BV CEO ) increases from 90 V at room temperature to 157 V at 250 8C.

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

“…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]).…”

Working toward high-power GaN/InGaN heterojunction bipolar transistors

“…The paradigm shift of III-N technology to III-N HBTs has not yet been realized over the last decades and was considered a territory of tremendous technological challenges. Although III-N HBTs have demonstrated striking performance in power handling capability [1,2], high-temperature and high-voltage operations [3,4,5] and microwave amplification [6], issues stemming from material growth techniques and device fabrication processing were left largely unexplored. III-N HBTs in the npn configuration are particularly challenging: the free-hole concentration of the Mg-doped p-type III-N layers is limited due to fundamental issues related to the deep Mg acceptor state, the lattice mismatch between epitaxial layers, and the use of foreign substrates are prone to threading dislocations and stacking faults; and the dry-etchinginduced nitrogen-rich surface leads to high p-type base contact resistance, just to name a few of the primary issues.…”

“…On the other hand, a latticematched substrate with higher thermal conductivity would be a suitable choice for high-J C HBTs. Several III-N HBTs grown on free-standing GaN substrates (FS-GaN) have been reported in recent years and these results have shown tremendous enhancement of current drive, common-emitter current gain and the dc power handling capabilities for either pnp AlGaN/GaN HBTs [14] or npn GaN/InGaN HBTs [2]. With these GaN/InGaN HBT demonstrations, it is evident that GaN/InGaN HBTs are a suitable choice of the widebandgap material system over AlGaN/GaN heterostructures for the 'first-generation' of III-N HBT technology.…”

III-N High-Power Bipolar Transistors

“…To the best of our knowledge, this report is the first RF demonstration of GaN/InGaN HBTs with f T > 5 GHz. We also reported a ultra-high d.c. power density of > 3 MW/cm 2 for an InGaN HBTs built on a free-standing (FS) GaN substrate (20).…”