Binding energy for the intrinsic excitons in wurtzite GaN

We present the results of an experimental study on the binding energy for intrinsic free excitons in wurtzite GaN. High-quality single-crystal GaN films grown by metalorganic chemical vapor deposition were used in this study. Various excitonic transitions in GaN were studied using reflectance measurements. The observation of a series of spectral features associated with the transitions involving the ground and excited exciton states allows us to make a straightforward estimate of exciton binding energy using the hydrogenic model. Our results yield a binding energy E(b) = 0.021 +/- 0.001 eV for the A and B excitons, and 0.023 +/- 0.001 eV for the C exciton in wurtzite GaN within the framework of the effective mass approximation.