Carrier mass measurements in degenerate indium nitride

We present photoluminescence measurements under intense magnetic fields (B up to 30 T) in n-doped indium nitride samples with carrier concentration ranging from about 7.5x10(17) cm(-3) to 5x10(18) cm(-3). The observation of transitions involving several Landau levels permits to determine the carrier-reduced mass mu around the Gamma point. Depending on the carrier concentration, we find mu ranging between 0.093m(0) and 0.107m(0) (m(0) is the electron mass in vacuum). This finding poses a lower limit to the electron effective mass, whose unexpectedly large value (m(e)>= 0.093m(0)) indicates that the sources of n doping in InN perturb strongly the crystal conduction band near its minimum.