Comparison of single- and double-barrier pseudomorphic InGaP/InGaAs HFETs

Abstract

We report the growth and fabrication of pseudomorphic InGaP/InGaAs/GaAs doped-channel heterostructure field effect transistors (HFETs). A direct comparison between single and double barrier HFETs of otherwise nominally identical devices shows that the use of a double barrier structure reduces the output conductance and enhances both the current gain cutoff frequency f T and the maximum oscillation frequency f max. The maximum drain current reaches 630 mA/mm for highly strained In 0.30Ga 0.70As channel devices compared with 360 mA/mm for comparably doped In 0.15Ga 0.85As channel HFETs. Compared to that of In 0.15Ga 0.85As channel devices, the In 0.30Ga 0.70As channel HFETs yield a higher maximum oscillation frequency while having a comparable current gain cutoff frequency. Double barrier HFETs with an In 0.15Ga 0.85As channel yield f T=19 GHz and f max=63 GHz, while those with an In 0.30Ga 0.70As channel show a result of 18 and 78 GHz, respectively. These results demonstrate that the use of highly strained InGaAs channels and double InGaP barriers significantly improves device performance.