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

We report the growth and fabrication of pseudomorphic InGaP/InGaAs/GaAs dop ed-channel heterostructure field effect transistors (HFETs). A direct compa rison between single and double barrier HFETs of otherwise nominally identi cal devices shows that the use of a double barrier structure reduces the ou tput conductance and enhances both the current gain cutoff frequency f(T) a nd the maximum oscillation frequency f(max). The maximum drain current reac hes 630 mA/mm for highly strained In0.30Ga0.70As channel devices compared w ith 360 mA/mm for comparably doped In0.15Ga0.85As channel HFETs. Compared t o that of In0.15Ga0.85As channel devices, the In0.30Ga0.70As channel HFETs yield a higher maximum oscillation frequency while having a comparable curr ent gain cutoff frequency. Double barrier HFETs with an In0.15Ga0.85As chan nel yield f(T) = 19 GHz and f(max) = 63 GHz, while those with an In0.30Ga0. 70As channel show a result of 18 and 78 GHz, respectively. These results de monstrate that the use of highly strained InGaAs channels and double InGaP barriers significantly improves device performance. (C) 1998 Elsevier Scien ce B.V. All rights reserved.