Research On The Materials Of Al_xGa_1-xN And AlN/GaN Grown By MOCVD And Their Devices

Ⅲ-nitride materials, represented by gallium nitride (GaN) and aluminum nitride(AlN), are direct and wide bandgap semiconductor materials, and have excellentchemical and thermal stability. This kind of semiconductors is widely used in thefield of optoelectronics and microelectronics due to their excellent optical andelectrical properties. Currently, however, Ⅲ-nitride materials which have beenmaturely applied to light emitting diodes (LED) and laser diodes (LD) and otheroptoelectronic devices are still in the research stage for ultraviolet (UV)photodetectors, especially solar-blind UV detectors this kind of optoelectronicdevices. In addition, in the field of microelectronics, the main research focuses onthe use of the advantages of strong breakdown electric field, high electron mobilityand high saturation drift velocity of Ⅲ-nitride materials, and fabricates high electronmobility transistors (HEMT) for the application in high-temperature, high-frequency,high-power and high-voltage electronic devices. However, the application of theⅢ-nitride materials in the nonvolatile memory device is almost in the researchblank.This thesis is divided into two parts. The first part, in the field of optoelectronicapplications, carrying out the comparative study between the front-and back-illuminated PIN structure solar-blind UV detectors to reveal the superiority ofback-illuminated structure and accumulate related technologies of focal plane array(FPA). The second part, in the field of microelectronic applications, carrying out thestudy of AlN/GaN heterojunction MIS structure devices and find that the devicepresents obvious regenerable bipolar resistive switching characteristics which have the potential application in rewritable nonvolatile memory device. Through intensivestudy, revealing its mechanisms. The main results of this thesis are as follows:1. The growth of high quality AlN templates as substratesDue to the lack of native substrate, AlN templates are good substrates forepitaxial growth of AlGaN materials. This thesis uses a two-step growth method togrow AlN on sapphire. In the growth process, using405nm shortwave in-situmonitoring to study the growth process and mechanism of AlN nucleation layerunder different growth temperature. Combining with characterization methods suchas atomic force microscopy (AFM), high resolution X-ray diffraction (HRXRD),transmission spectrum and Raman spectroscopy to study the overall performance ofcrystalline quality, crystal orientation, stress of AlN templates grown with differentnucleation temperature and obtain high quality AlN templates with atomic step,single crystal orientation, approximate stress-free to sever as substrates for thegrowth of PIN structure high Al content AlGaN materials.2. PIN structure AlGaN-based materials growth and device performance researchFirstly, carrying out the regulating growth and performance optimization ofintrinsic、N-type and P-type AlGaN monolayer on AlN templates. On this basis,designing the growth structure and parameters of PIN structure AlGaN-basedmaterials and growing the materials on the AlN templates which meet the designparameters well. Combining with device processing and preparing front-illuminatedPIN structure AlGaN-based unit detector and2×2array back-illuminated devices,and carrying out comparative study on the performance of front-andback-illuminated PIN structure AlGaN-based solar-blind UV detectors. The overallperformance of back-illuminated one is better than front-illuminated one. The pixelsof fabricated back-illuminated2×2array perform relative uniform property. Throughthe study, supplying references and technical reserves for the fabrication of PINstructure AlGaN-based solar-blind UV FPA.3. AlN/GaN heterojunction material growth and MIS device performance researchAlN/n-GaN heterojunction material is in-situ grown and Ni/AlN/n-GaN MISstructure device is prepared. It is found that the device performs regenerable bipolarresistive switching characteristics during the test process and reveals its mechanismthrough intensive study. This phenomenon can be used for regenerable nonvolatilememory device, and the device can be integrated with nitride HEMT to constructone-transistor-one-resistor (1T1R) integrated memory. The study will contribute to the development of in-situ epitaxial growth of Ⅲ-nitride materials for preparing allnitride material system memory devices used in optoelectronic integrated chip(OEIC).