High-speed kink-free InAlAs/InGaAs/InP field-effect transistors

A method to eliminate the “kink-effect” in InAlAs/InGaAs/InP heterostructure field-effect transistors with the use of a p-type back-gate is presented. DC measurements on fabricated devices show that the kink in the output characteristics can be almost completely eliminated in the back-gated devices. This is accomplished by removing holes generated by impact ionization and thereby eliminating the feedback that causes the enhancement in the output conductance. Temperature-dependent measurements of the front-gate current show that the bell-shaped signature of the impact-generated holes in the front-gate current has an activation energy of 260 meV, in good agreement with the confinement energy for holes in the valence band of the InGaAs channel. Small-signal measurements on the back-gated devices show that f_T is not reduced by the presence of the conducting back-plane, however, f_max decreases by 20% due to an increased capacitive coupling between the source and drain