Liquid Si ditertiarybutyl silane (DTBSi) metal-organic source was used as the Si dopant source for the growth of n-type GaN by metal-organic chemical vapor deposition (MOCVD) for the first time to replace the conventional gaseous Si sources like silane SiH4 [K. Pakula, R. Bozek, J.M. Baranowski, J. Jasinski, Z. Liliental-Weber, J. Crystal Growth 267 (2004) 1] and disilane Si2H6 [L.B. Rowland, K. Doverspike, D.K. Gaskill, Appl. Phys. Lett. 66 (1995) 1495]. Electrical, structural, optical, and surface properties of the samples doped by DTBSi as well as an undoped control sample are determined by Hall, high resolution X-ray diffraction (HRXRD), photoluminescence (PL), and atomic force microscopy (AFM) measurements respectively. A constant doping efficiency for GaN is obtained with carrier concentration up to 10(18) cm(-3). The typical HRXRD full-width at half-maximum values of symmetric (0 0 2) and asymmetric (10 2) planes are 284 and 482 arcsec, respectively. The near band edge PL intensity is found to be increased proportional to the doping concentration. Dark spot density is also determined,from AFM measurement. (c) 2006 Elsevier B.V. All rights reserved.