Electron heating in AlGaN/GaN and AlGaAs/GaAs two-dimensional electron systems

The thesis describes the electron heating in two-dimensional GaAs and GaN electron systems. This dissertation consists of the following two topics.

1. The relation between electron heating and current scaling in GaN/AlGaN two-dimensional electron system

We have measured the electron transport properties in a AlGaN/GaN heterostructure without magnetic field. We measured the longitudinal form 0.27 K to 60K as a self-thermometer. An insulator-like behavior is seen at low temperature. We also measured the longitudinal as a function varying with currents from 10^-7 A to 10^-4 A at a fixed lattice temperature 0.27 K. We obtained a current scaling relation, Te ~ I^a , and the electron energy loss rate, P ~ Te^n -TL^n. Finally, we picked the high-power regime to modify the effective carrier temperature as a function of current and energy loss rate.

2. The relation between electron heating and density of state in GaAs/AlGaAs two-dimensional electron system

We performed transport measurements on a GaAs/AlGaAs 2DEG as a function of magnetic fields at different temperatures and currents, respectively. We got the value a of the current scaling in the vicinity of filling factors v = 3, 5, 7, and 9 and at the filling factor v = 11. We observed that the longitudinal resistivity has a strongly asymmetric behavior in the spin-up regions. This phenomenon can be seen in a high mobility sample. We analyzed the activation energy to obtain the spin gap, the enhanced g-factor, and the critical field Bc. We also probed the low-field QHE and found the Landau-level spacing is much larger than the localization-induced mobility gap.