GaN/AlGaN based complementary p+-p−-p-n+ ATT-device for application in THz Imaging

A detailed simulation investigation is carried out on the hetero-structure complimentary (p⁺-p^--p-n⁺) IMPATT oscillator for Terahertz power generation. It is observed that this newly proposed GaN/AlGaN IMPATT may generate a pulsed power density of ~8×10¹⁰ Wm^-2 with an efficiency of 11%, whereas it´s flatly doped counterpart is capable of delivering a pulsed power density of only 3×10¹⁰ Wm^-2 with 7% efficiency. The total parasitic series resistance, R_S, including that due to the un-depleted region in device and also the effects of ohmic contact resistances, has been found to be a major problem that reduces the negative resistance significantly and thus it has a detrimental effect on THz oscillation of the device. The study reveals that the value of R_S decreases by 40% as the structure, semiconductor material pair as well as doping profile of the diode changes suitably from conventional to the proposed hetero-structure p⁺-p^--p-n⁺ type, by incorporating a 300A⁰ Al_0.4Ga_0.6N layer in the p-drift region. This first study will be a useful guide in the THz-sector to meet the ever-increasing demand of semiconductor THz-sources for application in Imaging or in improvised explosive device (IED) detection.