Observation of compensation in GaN films grown by metalorganic chemical vapor deposition

Hall-effect measurements were conducted on an unintentionally doped n-type GaN films grown on (0 0 0 1) sapphire substrates in a low-pressure metalorganic chemical vapor deposition (LP-MOCVD) system. Variable temperature Hall-effect measurements reveal a different dependence of the electron concentration and the Hall mobility on temperature for the two samples. In the sample with a background concentration of 10¹⁸ cm⁻³, the electron concentration shows a non-monotonous relationship with increasing temperature from 90 to 400 K. However, in the normal sample with a background concentration of <10¹⁷ cm⁻³, the dependence of the electron concentration on temperature is monotonous between 90 and 400 K. The different behavior was also found in the dependence of the Hall mobility on temperature for the sample. The experimental data were analyzed by considering two donor levels and one acceptor level model. The good agreement between measured data and calculation demonstrates that the abnormal dependence is indicative of a compensation effect in GaN film grown by LP-MOCVD.