710 GHz GaN gradient doped Schottky barrier diode with high breakdown voltage

In this work, a 710 GHz GaN Schottky barrier diode (SBD) with high breakdown voltage was proposed and fabricated. The high-frequency SBDs suffer from the trade-off between the frequency (fc) and breakdown voltage (Vbr). We solved this problem with the gradient doping technique, and the fc and Vbr were improved at the same time. For the proposed gradient doped GaN SBD, the doping concentration of the drift layer increases gradually from top to bottom. Then, the capacitance was reduced by the lightly doped surface region, while the series resistance was reduced by the heavily doped bottom region. As a result, fc was improved, and a high fc of 710 GHz was obtained. In addition, Vbr was also enhanced by the lightly doped surface region, and a high Vbr of 28 V was achieved. As a consequence, fc · Vbr of the proposed SBD is about 2 times that of the previous GaN SBDs, which is a great improvement. The gradient doping technology fully exploits the potential of GaN SBD in high frequency and high voltage, making GaN SBD a promising candidate for terahertz (THz) applications.