The electrical properties of AlInGaN/GaN heterostructures grown on sapphire substrate by metal-organic chemical vapor deposition under different V/III flux ratios from 3880 to 9082 were investigated. Rutherford backscattering and channeling were used to determine the composition and to evaluate crystalline quality of AlInGaN quaternary epilayers. Hall measurements at room temperature and 77 K showed that less sheet concentration and higher electron mobility were in lower V/III ratio samples. An intense photoluminescence at 351 nm with a narrow FWHM about 48.3 meV was assigned to be from Al0.08In0.015Ga0.905N layer grown under 3880 V/III flux ratio. With a comparison of Raman spectra of wafers of different V/III flux ratios and membranes on Si, local strain in AlInGaN layers were also discussed. Point defects were considered to be related with large local stress in GaN template layer under AlInGaN of high V/III flux ratio, which may decrease the electron mobility in AlInGaN/GaN heterostructures. (c) 2006 Elsevier B.V. All rights reserved.