Improved performance of Ni/GaN Schottky barrier impact ionization avalanche transit time diode with n-type GaN deep level defects

Abstract

Abstract In this paper, the effects of n-type GaN deep level defects on the DC, small signal AC, and radio frequency (RF) characteristics of Ni/GaN Schottky barrier impact ionization avalanche transit time (IMPATT) diode are investigated. A double avalanche termination region (DATR) structural IMPATT diode is proposed to mitigate the influences caused by these deep level defects. Simulation results show that the internal electric field, carrier generation rate and carrier velocity of IMPATT diode are affected by these deep level defects. With the increase of deep level defects density, the maximum RF output power, DC-to-RF conversion efficiency and optimum frequency of the diode all show a tendency to degenerate correspondingly. Through adjusting the electric field property properly of the diode, the DATR structural IMPATT diode improves the performances of IMPATT diode. The negative peak conductance of the improved diode is 11.4 × 103 S cm−2 at 248 GHz, showing the lowest quality factor of 1.42, the improved maximum RF output power of 1.35 MW cm−2 and DC-to-RF conversion efficiency of 15.7% at 220 GHz under the same deep level defects density, these characteristics of the improved DATR structural IMPATT diode reach the level which the low deep level defects density original diode shows.