Studies On Properties And Measurement Of AlGaN/GaN Based HEMT Materials

The High Electron Mobility Transistor (HEMT) is widely thought as the most competitive three-end apparatus in the field of microwave/millimeter wave devices and circuit. Because of its small noise and good power performance, it will totally change the present status of electronic equips which were used in army. But in the high-quality AlGaN/GaN heterostructure, there will be two dimensional electron gas (2DEG) system with high electronic density on the surface of heterostructure, even though all layers were undoped artificially. The HEMT based on the AlGaN/GaN heterostructure has excellent physical characters, such as wide energy band, high thermal conductance, high electron-saturation- excursion velocity, good thermal stabilization and so on, which makes it suitable for apparatus of high temperature, high voltage, high frequency and high power. Material epitaxy is the foundation of fabricating the power apparatus, and it affects the electronic characters. So for obtaining high performance device, we must develop good material system. And material epitaxy is the most important part in fabricating the semiconductor laser. At present, Metal Organic Chemical Vapor Deposition (MOCVD) technology has comparative high development level and high epitaxy quality.In this paper, we analyzed and calculated the theory of AlGaN/GaN HEMT, and got the theory on the growth of 2DEG and the source of 2DEG electrons. We also analyzed the factors which affect the 2DEG and carried through an experiment about it.We introduce the theory of MOCVD and the process of experiment. And we analyzed theories of Hall testing, X-ray Diffraction (XRD), Atomic Force Microscope (AFM) and mercury probe CV.We studied the material growth technologies of GaN epitaxial layer and AlGaN/GaN heterostructure on sapphire, and put up the epitaxial growth of HEMT material based on AlGaN/GaN heterostructure in different V/III ratio and doping concentration. We tested the characters of epitaxial materials which were grown in different condition, with the method of Hall testing, XRD, mercury probe CV and AFM, and obtained the result that material will have better electronic performance which was grown in such condition: theⅤ/Ⅲratio in AlGaN layer is 837, and the n+-AlGaN layer is doped with SiH4 of 7.5E+17cm-3 .