The electron effective mass in hexagonal GaN films grown by metal orga
nic vapor phase epitaxy on sapphire substrates is determined by cyclot
ron resonance experiments. Its value is m(p) = 0.22 +/- 0.005 m(o). T
aking polaron effects into account the band edge mass is m(b) = 0.20
+/- 0.005 m(o). From the resonance linewidth a mobility of 3500 cm(2)/
V . s at 6 K is obtained.