The effect caused by asymmetric structures on the performance of the AlGaN/GaN bilateral impact-ionizat-ionavalanche-transit-time (BIMPATT) device is studied in this article. The asymmetric structures include the asymmetry of the bilateral channel lengths by changing the anode position and the asymmetry of the two-dimensional electron gas (2DEG) concentrations by changing the AlGaN thickness. The asymmetry affects the direct current (DC), radio frequency (RF), and noise characteristics of the BIMPATT. Large-signal analysis shows that the asymmetric structures improve the operating frequency but reduce the maximum power and efficiency of the BIMPATT. The asymmetric structures show better RF characteristics than the symmetric structure in the high-frequency band. At last, the asymmetric structures increase the noise performance of the BIMPATT. The reason for these phenomena is the asymmetry of avalanche ionization region and intensity caused by the asymmetry of device structure. This article provides more references for the design and performance optimization of the lateral IMPATT devices.

In this article, a lateral AlGaN/GaN high-electron-mobility avalanche-transit-time (HEMATT) transistor based on the gate-structure (G-HEMATT) is first demonstrated. The presence of the gate changes the avalanche generation location and alters the current path to form a new effective channel for the avalanche transport mode, so the characteristics of G-HEMATT can be modulated according to the gate location. Our simulations show that the G-HEMATT exhibits better characteristics in terms of operating frequency, conversion efficiency, and AC power. The presence of the gate creates and changes the length of the dead zone, thus modulating the effective channel of the avalanche-transit mode. Compared to the HEMATT in this article, the optimum frequency of the G-HEMATT rises from 360 to 480 GHz, the maximum AC output power rises from 1.96 to 4.61 W/mm, and the maximum conversion efficiency rises from 11.21% to 22.03%. It is also found that the existence of the gate structure allows the formation of the new conducting channel between the gate and the drain, but the gate voltage has no significant effect on the device performance. The results also show that the sheet concentration of the channel two-dimensional electron gas (2-DEG) has a large effect on the performance of G-HEMATT, it is essential to ensure that the sheet concentration is not too low in order to obtain a more effective improvement in device performance.

In this paper, three polytypes of p-(6H, 4H, 3C)SiC and n-GaN heterojunction single-drift (SDR), and double-drift (DDR) impact-ionization-avalanche-transit-time (IMPATT) diodes are studied. We conduct the numerical simulations of the direct current (DC), radio frequency (RF), and noise characteristics of IMPATT diodes The results show that (6H)SiC/GaN IMPATT diodes have the optimum RF characteristics. Among them, the RF power density of (6H)SiC/GaN DDR IMPATT diode can reach 2.23 MW/cm2. The DC-RF conversion efficiency of (6H)SiC/GaN SDR IMPATT diode can reach 23.4%. Their noise performances are being examined in the meantime. The (3C)SiC/GaN IMPATT has better noise characteristics in the SDR structure, while (4H)SiC/GaN IMPATT has better noise characteristics in the DDR structure. This study provides a reference for the design and fabrication of IMPATT diodes.