Electron effective mass in hexagonal GaN

Far-infrared magneto-optical investigations of shallow donors in epitaxial GaN layers on sapphire were carried out by means of Fourier transform spectrometry up to 23 T. From the splitting of the donor p states in a magnetic field, the cyclotron effective mass for conduction electrons was found to be $m^{*}\text{=0.222\hspace{0.05em}}{\mathrm{m}}_{\mathrm{0}}.$ A precise determination of the mass was made possible by the high quality of the spectra and by taking into account high magnetic field data above 12 T.