Carbon -: an alternative acceptor for cubic GaN

Carbon doping of cubic GaN epilayers has been performed by rf-plasma-assisted molecular beam epitaxy using an e-beam. evaporation source. Hall-effect measurements at room temperature and low-temperature photoluminescence. were used to characterize the electrical and optical properties. Room-temperature Hall-effect measurements revealed a maximum hole concentration of the c-GaN epilayer of 6 x 10(17) cm(-3) with a mobility of 200 cm(2) V-1 s(-1). With increasing e-beam evaporation power a new photoluminescence. line at 3.08 eV appeared at 2 K. This line is attributed to a donor acceptor transition, which involves the shallow C-N acceptor. From the spectral position the binding energy of the C acceptor is estimated to be about E-C = 0.215 eV. At high C concentrations a deep band appeared at 2.1 eV indicating compensation effects.