A low insertion loss GaAs pHEMT switch utilizing highly n+-doping AlAs etching stop layer design

This study reports, for the first time, AlGaAs/InGaAs/AlGaAs high-electron mobility transistors (HEMTs) devices and single-pole-single-throw (SPST) switches with utilizing n⁺-type doping on etching stop AlAs layer (M-HEMTs) designs were fabricated and investigated. We doping on etching stop AlAs layer to reduce parasitic resistances and enhance device DC and RF power performance. These modified M-HEMTs(HEMTs) demonstrated an Sheet resistance (R_sh) is 65.9 Ohms/sq(71.9 Ohms/sq), maximum I_ds is 317.8 mA/mm(290.3 mA/mm), transconductance(g_m) is 259.3 mS/mm(252.1 mS/mm), cut-off frequency(f_T) and maximum frequency(f_max) are 19.4 GHz(18.1 GHz) and 58.6 GHz(45.9 GHz), a power-added efficiency of 33.4 %(30.6 %), and a linear power gain of 13.1 dB(10.3 dB) for an 1.0 mum gate-long device under a 2.4 GHz operation. In addition, both off-state capacitance and the specific on-resistance (R_on) of HEMT are dominated factors which are sensitive to doping n⁺-type on etching stop layer for RF switch applications. The SPST switches on-state an insertion loss of 1.42 dB(1.68 dB), the off-state an isolation of 13.02 dB(11.42 dB). These characteristics suggest that utilizing n⁺-type doping on etching stop AlAs layer provide a better device and switches performances improvement.