Studying average electron drift velocity in pHEMT structures

Small-signal characteristics of pseudomorphic high-electron-mobility transistors based on donor–acceptor doped heterostructures (DA-pHEMTs) are compared to those of analogous transistors (pHEMTs) based on traditional heterostructures without acceptor doping. It is established that DA-pHEMTs, under otherwise equal conditions, exhibit (despite lower values of the low-field mobility of electrons) a much higher gain compared to that of usual pHEMTs. This behavior is related to the fact that the average electron drift velocity under the gate in DA-pHEMTs is significantly (1.4–1.6 times) higher than that in pHEMTs. This increase in the electron drift velocity is explained by two main factors of comparable influence: (i) decreasing role of transverse spatial transfer, which is caused by enhanced localization of hot electrons in the channel, and (ii) reduced scattering of hot electrons, which is caused by their strong confinement (dimensional quantization) in the potential well of DA-pHEMT heterostructures.