Back doping design in delta-doped AlGaN/GaN heterostructure field-effect transistors

In this paper, we investigate theoretically the electron transport in AlGaN/GaN single-barrier and in AlGaN/GaN/AlGaN double-barrier heterostructures, aimed to operate as high-power and high-temperature field-effect transistors. The presence of spontaneous and piezoelectric polarizations as well as the heterointerface polarity are evoked and taken into account in the modelling part. Delta-doping is used as a source of electrons for the channel quantum well. Calculations of the electron-band parameters are made by using self-consistent solutions of coupled Schrodinger-Poisson equations. It is found that the polarization fields act to significantly increase the two-dimensional sheet charge concentration. Moreover, the AlGaN/GaN heterostructures with higher Al compositions are found to be favourable for higher electron densities. On the other hand, the employment of a back doping with delta-shaped profiles is shown to improve further the electrical behaviour of the field-effect transistors studied.