Characterization of Graded Pulse-Doped Channel AlGaAs/InGaAs/GaAs Heterojunction Field-Effect Transistors

Abstract

This paper reports on the fabrication and characterization of graded pulse-doped channel AlGaAs/InGaAs/ GaAs heterojunction field-effect transistors (HFET's). Triple pulse-doped sheets, δ(n 1)=1.2×1012, δ(n 2)=4×1011, δ(n 3)=1×1011 cm-2 from buffer to gate is used as an active channel. Typical drain-to-source and gate-to-drain breakdown voltages are larger than 25 V. The further enhancement in breakdown voltage is using the following methodology: 1) a strained AlGaAs insulator, 2) an InGaAs quantum-well like channel, and 3) less impurity scattering in the graded pulse-doped channel. The maximum transconductance is 160 mS/mm with an available current density of 250 mA/mm. Further increasing the δ(n 1) to 4×1012 cm-2, the maximum transconductance is 165 mS/mm. The available current density is increased to 480 mA/mm. Moreover, their transconductance vs. gate voltage profiles display broad plateaus. The fabricated devices exhibit a small output conductance of 0.3 mS/mm. The evaluated open-drain voltage gain is as high as 500. These results have better performances than those of i-AlGaAs/n+-InGaAs HFET's fabricated by our system.