Improvement in reliability of InP-based HEMTs by suppressing impact ionization

We have improved the reliability of InP-based high electron mobility transistors (HEMTs) by using two structures that suppress impact ionization: a lattice-matched composite channel InGaAs/ InAlGaAs structure and a double-doped structure. In the composite channel structure, electrons transfer from InGaAs to InAlGaAs when the electric field is strong, thereby suppressing impact ionization under high drain bias. In the double-doped structure, the intrinsic built-in filed of the channel is smaller that it is in the conventional structure. The total electric field under a given drain bias voltage is therefore weaker, and this weaker field causes less impact ionization. Aging tests confirmed that both structures improved device reliability at a V_ds of 2 V.