High efficiency CW transferred-electron oscillator with optimized doping profile

This study is aimed at helping to design X-band CW transferred-electron oscillators with higher performance. Temperature rise in devices operating in the accumulation layer mode is analyzed both with heat sink negative and heat sink positive. Efficiencies and output powers in both polarities are calculated and compared. The calculation shows efficiency in CW operation is drastically improved by quantitatively controlling the doping profile to account for the temperature profile and further governed by carrier concentration times layer thickness (n × l) product and diode size. For the heat sink negative, output power over 800 mW is predicted from a single-mesa conventional structure, using a wafer with an n × l product of 2.0 × 10¹²cm^-2and doping profile increasing, toward the substrate (away from the heat sink), by 30-35 percent across the active layer. For the heat sink positive, an almost flat profile is suitable and output power over 1.5 W is predicted for a diode with a doping increase of 10 percent across the active layer toward the substrate. The calculations are substantiated experimentally by diodes with n × l products of 1.5-2.3 × 10¹²cm^-2and doping increases of 20-70 percent across the active layer toward the substrate heat sink negative operation.