Optical properties of n-doped (Si) hexagonal Ga1-xMnxN films (x=0.015) grown by metal-organic chemical-vapor deposition (MOCVD) on c-plane sapphire substrates have been studied by infrared reflectance spectroscopy. The effect of free carriers on GaMnN optical phonons, namely E-1(LO) and E-1(TO), is explored. It is found that the frequency of E-1(LO) increases with increasing free carrier concentration. The absorption coefficient (alpha) is calculated for the 200-2000 cm(-1) range and the maximum value of alpha is found to be similar to 10(5) cm(-1) at a frequency of 560 cm(-1). With increasing free carrier concentration, the FWHM of the absorption peak increased by 35%-40% as compared to an unintentionally doped (< 1x10(16) cm(-3)) film. (C) 2008 American Vacuum Society.