Hot electron power loss mechanisms in AlGaN/GaN heterojunctions

Hall effect measurements on AlGaN/GaN heterojunctions grown by a metalorganic chemical vapor deposition (MOCVD) technique have been carried out as a function of temperature in the range between 1.8 and 275 K at a fixed magnetic field. The experimental data have been used to calculate the longitudinal optical (LO) phonon energy.The experimental data for the temperature dependence of Hall mobility were compared with the theoretical formula for scattering mechanisms taken from the literature. In the numerical calculations, polar optical phonon scattering, ionized impurity scattering, background impurity scattering, interface roughness scattering, piezoelectric scattering, acoustic phonon scattering, dislocation and alloy disorder scattering were taken into account. It is concluded that alloy disorder scattering is the dominant scattering mechanism at low temperatures and polar optical phonon scattering is dominant at high temperatures.Shubnikov?de Haas (SdH) oscillations have been used to investigate the electronic transport properties and power loss mechanisms of two-dimensional (2D) electrons in AlGaN/GaN heterojunctions. The SdH oscillations were obtained from the measured magnetoresistance Rxx(B) by taking the second derivative of the raw experimental data. The 2D carrier density and the Fermi energy with respect to subband energy (EF?E1) have been determined from the period of the SdH oscillations. The in-plane effective mass (m*) and the quantum lifetime (?q) of 2D electrons have been obtained from the temperature and magnetic field dependences of the SdH oscillation amplitude, respectively.