High-breakdown AlGaAs/InGaAs/GaAs PHEMT with telluriumdoping

The authors report the fabrication and characterisation of an Al0.43Ga0.57As/In0.2Ga0.8As/GaAs pseudomorphic HEMT (PHEMT) with high channel conductivity grown by solid source MBE. The high conductivity of the channel is a direct consequence of the high sheet charge and high mobility that has recently been obtained by using tellurium as the n-type dopant in 43% AlGaAs. The device characteristics reflect the resulting reduction in the parasitic resistances of the high channel conductivity. Microwave measurements yield a short-circuit current gain cutoff frequency fT of 11 GHz and maximum oscillation frequency fmax of 25 GHz. A high gate-drain breakdown voltage of 26 V along with a maximum drain current density of 400 mA/mm obtained in the device illustrate the applicability of this technology in microwave power field effect transistors.