Performance of capless self-aligned gate D- and QE-mode p-HEMTs

Characteristics of 0.2 mum depletion mode (D) and quasi-enhancement mode (QE) capless InAlAs/InGaAs p-HEMTs having a self-aligned gate (SAG) are reported. The QE SAG capless p-HEMT showed improved output conductance and subthreshold characteristics due to the increased gate-to-channel aspect ratio implemented by using a buried Pt technology. The maximum g_m, I_ON/I_OFF, sub-threshold slope, f_tau, and f_max of the QE SAG capless p-HEMT were 1.22 S/mm, 2.11 times 10⁵, 65 mV/dec, 210 GHz, and 250 GHz and those of the D SAG capless p-HEMT were 1.12 S/mm, 1.27 times 10⁴, 78 mV/dec, 185 GHz, and 225 GHz, respectively. The QE SAG capless p-HEMT also exhibited a shorter drain delay time than the D SAG capless p-HEMT by about 46%.