The mobility and the carrier concentration of the epitaxial n-GaN are obtained experimentally as a function of the temperature between 300 and 15 K, and are found to be in good agreement with those derived from the numerical analyses assuming a certain amount of the compensation ratio. The sample available at present has a rather poor mobility compared with that expected from an ideal perfect crystal, and we must assume a comparatively large amount of the compensation in the numerical analyses. The typical 1/f noise characteristics are also observed by forming an ideal Ohmic contact to the devices at the optimum alloying temperature and its period. Based on the introduced amount carrier concentration and the mobility together with the contact conditions, the Hooge noise parameters are derived experimentally between 100 and 300 K. Experimental data reported so far are also summarized as a function of the normalized mobility. (c) 2005 Elsevier Ltd. All rights reserved.