Strain relaxation and thermal effects on the drain conductance in AlGaN/GaN HEMT

In this work the effects of technological and electrical parameters of Al_mGa_1-mN/GaN High Electron Mobility Transistors (HEMT) on the output conductance "gd" was studied in the first part. In the second part, the effect on gd of thermal and self heating in the device was analyzed. This study was made by taking into account the effects of spontaneous and piezoelectric polarizations in the heterojunction AlGaN/GaN and the relaxation of the crystal lattice induced by the aluminum mole fraction. An analytical model for the electrons concentration "ns" in the 2DEG and the current Ids in the channel for strong inversion regime was presented. By solving the Poisson equation and Schrödinger self-consistent calculations, including the spontaneous and piezoelectric polarizations, lattice relaxation, self heating and thermal effects the current I_ds was calculated. The output conductance g_d according to the voltage V_ds are deduced thanks to the analytical description of the calculated current I_ds.