The MOCVD Growth And Dislocation Research Of GaN Material

Gallium Nitride is the third generation semiconductor material after silicon and gallium-arsenide, and it has a large band gap, high breakdown voltage, high carrier saturation mobility and other excellent properties. Gallium Nitride has the unique advantage in semiconductor light emitting devices, detector, photovoltaic devices and high electron mobility transistor device. However, GaN material is facing many problems. There are no suitable substrate materials and when the electron concentration reaches 1019cm-3 level, the material defects will increase and the structural performance will be degraded. At the same time, the spontaneous polarization and piezoelectric polarization effect in GaN material can effect the device performance. So the study of nonpolar and semipolar GaN materials has important significance. In this paper, the epitaxy growth of heavily doped GaN and nonpolar GaN are studied, and the main work is as follows:1.The effects of SiH4 flux on the optical properties, crystal quality, electrical properties and surface morphology of heavily doped GaN materials are studied using MOCVD under different SiH4 flow. Based on the optical fluorescence test, XRD test, Hall test and other GaN materials characterizing methods, the mechanism of restraining the yellow luminescence by different SiH4 flux in heavily doped GaN is studied. The heavily doped GaN gets carrier concentration 6.4?1019cm-3, the FWHM of(0002) plane 339 arcsec, the FWHM of(1002) plane 273 arcsec when the SiH4 flow is 20 sccm.2.To improve the surface morphology of the heavily doped GaN material, the effects of SiH4 doping methods on thesurface roughness, crystal quality and optical properties are studied, combined with defect-selective etching method to study the amount of dislocation and the type of dislocation. By using delta doping way the GaN gets the square root roughness 6.17 nm, carrier concentration 3.06?1019cm-3, the FWHM of(0002) plane 269 arcsec, the FWHM of(1002) plane 343 arcsec.3.In order to obtain better nonpolar GaN material, the In Al N/GaN superlattice structure is used. The nonpolar GaN materials are grown with the superlattice structure, and the surface morphology of the materials are studied by optical microscope. The crystalline quality of the materials are analyzed using HRXRD. The FWHM of the nonpolar GaN containing the superlattice structure is 911 arcsec.4.The etching behavior of nonpolar GaN materials are studied. The different etching characteristic of nonpolar GaN material and polar Ga N material are explained, and the reasons for the etched groove are explained.5.The effect of buffer layer growth time on the surface morphology and etching characteristics for semipolar(11-22) GaN material is studied.