Piezoelectric doping and elastic strain relaxation in AlGaN–GaN heterostructure field effect transistors

We calculate the sheet electron density induced by the piezoelectric effect in AlxGa1−xN–GaN heterostructure field effect transistors. This density is limited by the elastic strain relaxation, which depends on AlGaN barrier layer thickness and on the Al molar fraction in the barrier layer. Piezoelectric doping is more important in structures with larger Al content and thinner barrier layers. These results agree with our experimental data.