Carrier confinement and feed-back correlation in InAlAs/InGaAs HEMTs on InP substrate

The RF behavior of InP-based HEMT structures was evaluated using a feedback correlation. No evidence was found that the deep quantum well InAlAs/InGaAs/InAlAs configuration adds to improved feedback behavior through additional confinement of hot carriers. The model does show that a drift region with a large aspect ratio can develop, which can be traversed by electrons with overshoot velocity leading to high f_max/f_T ratios at high f_T in the devices. It is concluded that in the design of millimeter-wave InP-based HEMTs, the structural aspect ratio and the aspect ratio of the drift region at the bias region of operation have to be optimized to take maximum advantage of a long drift region combined with a high transit overshoot velocity in the device