The following research describes low- temperature- grown (LT) GaN films grown by metallorganic vapor- phase epitaxy. Hall- effect measurements indicate that the resistivity of as- grown and annealed LT GaN films exceeds 10(11) Omega/square. LT GaN films exhibit no drastic change in properties even after 1100 S C postgrowth thermal annealing, unlike LT GaAs, whose resistivity is altered significantly by thermal annealing. However, the electrical properties of LT GaN can be easily altered by Si ion implants combined with thermal annealing. Implantation conditions can differ in order to convert LT GaN films from a semi-insulating material into an n- type material with a sheet carrier concentration of 8.8 x 10(13) cm(-2) similar to 4.5 x 10(14) cm(-2). Additionally, carrier transport in Si- implanted LT GaN films dominated by impurity band conduction was assumed to be caused by a high- density impurity level. Transmission spectra investigations of the LT GaN films indicated a region of gradual transition near the bandgap, because the film quality was poor as compared to high- temperature- grown GaN. Therefore, these films exhibited no distinct bandgap. (c) 2005 The Electrochemical Society.