A technique for optimizing construction of Ka-band power GaN/AlGaN HEMTs

A new technique for optimizing the construction of power HEMTs (selection of unit channel width d and the number of sections N, etc.) is proposed and experimentally investigated. It consists in measuring (or simulating) microwave characteristics of the set of passive transistor structures with different values of d and N. Passive structures include all the metal elements of the HEMT, but does not contain the active layer. The approach facilitates the optimization of the HEMT construction due to a simpler and faster fabrication of the test transistor structures. Good RF properties of Ka-band power 0.25 µm GaN / AlGaN HEMTs on SiC substrate are shown to have been achieved with d = 80−100 µm and N = 2−4.