| 초록 |
In recent years, related III–V(Nitrides) have attracted substantial scientific and industrial interest mainly due to its excellent properties. Among nitride alloys, the ternary AlGaN is needed for fabricating electronic devices such as AlGaN/GaN hetero-structure field effect transistor(HFET), high-power electronic devices and high-speed electronic devices operating at high temperature and hostile environments. But there always exist uniform or nonuniform strain in hetero-structures which may mainly originate from lattice mismatch and different thermal expansion coefficients between the epilayer and substrate. The strain status and the degree of strain relaxation in the AlGaN/GaN hetero-structures should be an important factor as well as the intrinsic piezoelectricity to exert a substantial influence on the concentration and distribution of the two-dimensional electron gas (2DEG) at the hetero-interface and thereby to influence the operation performance of the HFETs significantly. From this viewpoint, it will be important to investigate properties of AlGaN/GaN hetero-structures as Growth condition in optimizing the fabrication technology and design of related devices. The AlGaN/GaN hetero-structure were fabricated by metal-organic chemical vapor deposition. AlGaN/GaN hetero-structures were grown at different growth condition such as thickness of AlGaN layer, chamber pressure, NH3 flow rate. Auger Electron Spectroscopy(AES) and Atomic Force Microscopy (AFM) were used to investigate the surface state of AlGaN/GaN layers. Mobility of AlGaN/GaN epilayer were measured by Hall measurement. From these analysis result, we found out the optimized Growth condition of AlGaN/GaN hetero-structures. To investigate the characteristics of AlGaN/GaN hetero-structures, AFM, AES, TEM, I-V, Hall measurements were employed to analyze the change in structural and electrical properties. |
