Unintentionally doped GaN were grown on Si (111) substrates by metal organic chemical vapor deposition (MOCVD). The high-resolution X-ray diffraction (HRXRD) and Lehighton contactless sheet resistance measuring systems were employed to characterize the quality and sheet resistance (Rs) of GaN epilayer. The threading dislocation density (TDD) was estimated by calculating the full width at half maximum (FWHM) of GaN (0002) and (10-12) diffractions measured by HRXRD. The relationship between Rs and TDD in GaN epilayer was investigated. The influence of growth conditions of bottom GaN initial layer including carrier gas category (H2 or N2), growth temperatures, and growth pressures on the quality or resistivity of top GaN epilayer was discussed and analyzed. As a result, the improved resistivity was achieved in top GaN epilayer with low TDD by using H2 carrier, low growth temperature of 1050℃, and high growth pressure of 400mbar during the growth of bottom GaN initial layer.
Source:Jinglong Bu, Zhengyi Jiang and Sihai Jiao