Temperature effect on the submicron AlGaN/GaN Gunn diodes for terahertz frequency

Abstract

The wurtzite AlGaN/GaN Gunn diode with tristep-graded Al composition AlGaN as hot electron injector is simulated by using an improved negative differential mobility model of GaN. The results show that the oscillation mode of Gunn diode gradually shifts from dipole domain mode toward accumulation mode with increase in temperature, and the mode shift closely depends on the injector length. At the temperatures of 300–400 K, 0.6 and 0.4 μm Gunn diodes normally generate the oscillation of dipole domain mode, yielding the fundamental oscillation frequencies of 332–352 GHz and 488–508 GHz, respectively, with the dc/rf conversion efficiencies of 2%–3% and the output power densities of 109–1010 W cm−3. At higher temperatures, the diodes generate the accumulation mode oscillation, and the highest frequency approaches 680 GHz and 977 GHz, respectively, with the dc/rf conversion efficiencies of 0.5%–1%.