Determination of the polarization and strain distribution in AlGaN/GaN heterostructure field-effect transistors

In AlGaN/GaN heterostructure field-effect transistors (HFETs), the polarization Coulomb field scattering is determined by the ionized surface states of the AlGaN barrier layer surface and the additional polarization charges at the AlGaN/GaN interface. Based on the experimentally obtained 2DEG electron mobility and taking into account several main scattering mechanisms, especially polarization Coulomb field scattering, an iterative calculation method is proposed to determine the polarization and strain distribution under different bias voltages in the fabricated AlGaN/GaN HFETs, and a relationship is presented to connect the additional polarization/strain, the voltage drop through the gate Schottky barrier, and the device size. Based on this relationship, the strain energy in the AlGaN barrier layer is analyzed, and it is found that the total strain energy remains approximately constant.