On the possible effects of AlGaAsSb growth parameters on the 2-DEG concentration in AlGaAsSb/InGaAs/AlGaAsSb QW's

The absence of pinchoff in the room temperature current-voltage characteristics of certain AlGaAsSb/InGaAs/AlGaAsSb-based high electron mobility transistors (HEMT's) is investigated by theoretical calculations. The room temperature pinchoff properties are strongly affected by the Al mole fraction in the buffer layer, the In mole fraction in the channel, the unintentional acceptor doping level of the lattice-matched quaternary buffer, and the quantum well width. The use of InAs as the channel material imposes strict conditions on the composition and the unintentional acceptor doping of the buffer layer. With decreasing In mole fraction, the restriction is relaxed. A higher Al mole fraction in the buffer, along with a lower In mole fraction in the channel, results in superior pinchoff characteristic and lower gate leakage.