Vertically scaled GaN/AlN DH-HEMTs with regrown n+GaN ohmic contacts by MBE

GaN based HEMT device performance has been steadily improving, offering a combination of high electron velocity and high breakdown field. This makes them a prime candidate for high performance millimeter-wave solid-state power amplifiers (PAs). Further improving high frequency performance requires not only laterally scaling the gate length but also vertically scaling the barrier thickness. Scaling the device, however, must not come at the expense of increased access resistance. The GaN/AlN material system is suitable for vertical device scaling since it provides a high electron density in the channel while reducing the barrier thickness. However, due to AlN's large band gap, a low contact resistance between electrodes and the channel is difficult to achieve. In fact, a high on-resistance (Ron) of >2.0Ω·mm has been reported for GaN/AlN HEMTs using conventional alloyed ohmic contacts [1]