InP-based enhancement-mode pseudomorphic HEMT with strained In/sub 0.45/Al/sub 0.55/As barrier and In/sub 0.75/Ga/sub 0.25/As channel layers

Using strained aluminum-rich In/sub 0.45/Al/sub 0.55/As as Schottky contact materials to enhance the barrier height and indium-rich In/sub 0.75/Ga/sub 0.25/As as channel material to enhance the channel performance, we have developed InP-based enhancement-mode pseudomorphic InAlAs/InGaAs high electron mobility transistors (E-PHEMT's) with threshold voltage of about 170 mv. A maximum extrinsic transconductance of 675 mS/mm and output conductance of 15 mS/mm are measured respectively at room temperature for 1 μm-gate-length devices, with an associated maximum drain current density of 420 mA/mm at gate voltage of 0.9 V. The devices also show excellent rf performance with cutoff frequency of 55 GHz and maximum oscillation frequency of 62 GHz. To the best of the authors' knowledge, this is the first time that InP-based E-PHEMT's with strained InAlAs barrier layer have been demonstrated.