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 spect rometry 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 b e m(*) = 0.222 m(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. (C) 1999 American Institute of Physics. [S0003-6951 (99)01852-5].