High breakdown voltage InGaAs/InAlAs HFET usingIn 0.5 Ga 0.5 P spacer layer

A highly strained In0.5Ga0.5P spacer is introduced into an HFET grown by MOVPE on InP substrate for the first time. Despite the large lattice mismatch and the group V exchange at the channel-spacer interface the transport data are not affected (µH, 300K = 11 300 cm2/Vs, ns = 2 x 1012 cm-2). However the large bandgap energy of InGaP results in improved gate leakage, drain-conductance and drain breakdown. At VDS = 10 V a voltage gain of vu > 100 is maintained. HFETs with Lg = 0.7µm exhibit gm = 360 mS/mm, ID, max(VDS = 6V) = 550 mA/mm and a cutoff frequency fmax of 150 GHz. At VDS = 5.5V an AC output power of 0.6 W/mm is achieved indicating the capability for high power HFET application on InP substrates.