High-efficiency enhancement-mode power heterojunction FET with buried p/sup +/-GaAs gate structure for low-voltage-operated mobile applications

This letter describes a successfully developed enhancement-mode double-doped AlGaAs/InGaAs/AlGaAs heterojunction FET with a buried p⁺-n junction gate structure for low-voltage-operated mobile applications. The buried p⁺-GaAs gate structure effectively reduced on-resistance (R_on) and suppressed drain-current frequency dispersion for the device with high positive threshold voltage, resulting in high-efficiency characteristics under low-voltage operation. The fabricated p⁺-gate HJFET exhibited a low R_on of 1.4 Omegamiddotmm with a threshold voltage of +0.4 V. Negligible frequency dispersion characteristics were obtained through pulsed current-voltage measurements for the device. Under a single 2.7-V operation, a 19.8-mm gate width device exhibited a power added efficiency of 51.9% with 26.8-dBm output power and a -40.1-dBc adjacent channel power ratio using a 1.95-GHz wideband code-division multiple-access signal