Improvement in Device Performances of InP-Based HEMTs by Thinning a Barrier Layer

Abstract

The dependences of source resistance, R_s, transconductance, g_m, gate capacitance, C_gs, C_gd, and cutoff frequency, f_T, of InP-based HEMTs on an InAlAs barrier layer thickness, d, were investigated. We divided R_s into 4 elements and analyzed the effect of thinning a barrier layer. The resistance originated from the large band discontinuity between InAlAs and InGaAs decreased by thinning a barrier layer, while the resistance in the gate-recessed region increased. As a result, InP-based HEMT with d=10 nm showed lowest R_s. On the other hand, g_m increased monotonically with d, due to the reduction of the gate to channel distance, and g_m^int reached to 2.6 S/mm at d=5 nm. We also estimated f_T by using small-signal measurements. f_T increased with the reduction of d, which results in the improvement in noise characteristics.