GaN planar Gunn diodes with high–low sheet density distribution of 2DEG for terahertz application

This paper investigates a GaN planar Gunn diode with regions of high–low two-dimensional electron gas (2DEG) sheet carrier density. By altering the length of the high 2DEG sheet density region (H-region), this diode achieves a large increase in the operating frequency compared to conventional planar Gunn diodes of the same size, while retaining the power output. Under certain conditions, it can potentially double the frequency of conventional planar Gunn diodes. This research studies the length and sheet density characteristics of the H-region and the mechanisms by which they affect device performance. For the device with a low-density region length of 0.6 μm, a minimum H-region length of 0.2 μm is required to increase the output frequency from 518.16 to 926.28 GHz. For a low-density region length of 0.5 μm, an H-region length of 0.3 μm or more is required to reach a device frequency of 1.149 THz, all while maintaining the DC-to-AC conversion efficiency at about 1.63%. Instead of simply reducing device sizes, this study employs a step-like structural design to significantly increase the device's upper frequency limit and operating frequency.