Growth Of GaN-based Heterostructure Materials On High Temperature AIN Nucleation Layer

GaN-based heterostructures are currently the most important and most essential structures for developing electronic devices for high temperature, high frequency and high power applications. Presently, GaN and AlxGal-xN heterostructure materials and devices have attracted a lot of interests. In this paper, mechanism of background carrier generation in GaN with different low temperature nucleation layer is systematically studied by MOCVD. The effect of Fe doping on the AlGaN/GaN heterostructure is also studied. Also we studied how the high-temperature AIN nucleation layer influences on the AlGaN/GaN heterostructure. The main results are as follows:1. Morphology of nucleation layer (NL) is achieved at different growth rate by means of metal organic chemical vapor deposition (MOCVD). The effect of NL morphology on surface quality and crystal quality of main GaN and AlGaN/GaN heterostruture electronic prosperity is studied. The results of experiment show that nucleation island with large size and high density is helpful to high crystal quality AlGaN/GaN heterostruture. Temperature also influence the surface and crystal quality of main GaN. There are many pits on the surface of GaN when the temperature is too low and there are many hexagonal defects on GaN surface when temperature is too high. We also research the relationship of thickness of GaN with its crystal quality. When the thickness of GaN is more than 1200nm GaN will has good crystal quality and morphology. A research on the AlGaN/GaN heterostructures grown on the vicinal sapphire substrates is presented in this paper. Superior structural and electrical properties of AlGaN/GaN heterostructures are obtained by using vicinal substrates, and high performance AlGaN/GaN materials are finally developed by combing the vicinal substrates and optimized growth processes.2. The source of background carrier in GaN and the method of growth high resistivity GaN are investigated. The mechanism of background carrier generation in GaN with different nucleation layer is studied though the analysis of C and O atom in GaN. Fe-doping in GaN is also investigated. The high crystal quality and good electronic property AlGaN/GaN heterstructure is achieved by process optimization.3. The effect of growth condition of high temperature AIN on AlGaN/GaN heterostruture is investigated. The high crystal quality of AIN template is achieved by the initially alternating supply of ammonia (IASA) method. The results of AFM about surface of AIN show that HT-AlN is consisted of high density taper shape island. This structure is helpful to the growth of AlGaN/GaN heterostructures. The use of AIN by the IASA method cans effectively increase the crystalline quality and surface morphology of GaN. The mobility and concentration of 2DEG of AlGaN/GaN heterostuctures was also ameliorated. 4. The influence of the thickness of AlGaN barrier layer on the surface of GaN and its electronic property is investigated. High electronic property AlGaN/GaN heterostruture is achieved by process optimization. Energy band diagram and carrier distribution characteristics for various types of GaN-based double-heterostructure are simulated by solving the one-dimensional self-consistent Schrodinger-Poisson equation. Double-heterostructure with different barrier thickness is grown. AlGaN/GaN/AlGaN double-heterostructure without parasitic channel is achieved by optimizing growth condition.