Optimization of aluminum gallium nitride growth by molecular beam epitaxy and its effect on electron mobility in a two-dimensional electron gas.

摘要

The III-nitride system offers the possibility of producing high power/high temperature field effect devices that are currently unavailable otherwise. One of the basic components of these devices is a 2 dimensional electron gas (2DEG) and this thesis deals with the growth and optimization of the AlGaN/GaN towards the optimization of the 2DEG using molecular beam epitaxy (MBE).; The AlGaN growth was investigated using MBE and found to be coherent on the GaN template with its composition determined solely by the Al flux. A method of determining composition by x-ray diffraction was developed. The best growth regime was found to be Ga-stable growth conditions (high Ga/N ratios) at 750°C as determined by surface structure, low temperature mobility and impurity incorporation. Scattering mechanisms were also investigated. The two-dimensional electron gas was determined to be in the MBE grown material at the AlGaN/GaN interface and at low temperatures was found to be the only conducting layer in the structures. Quantum transport effects were observed thus indicating the high quality of the structure.