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-cryst al GaN films grown by metalorganic chemical vapor deposition were used in this study. Various excitonic transitions in GaN were studied usin g reflectance measurements. The observation of a series of spectral fe atures associated with the transitions involving the ground and excite d exciton states allows us to make a straightforward estimate of excit on binding energy using the hydrogenic model. Our results yield a bind ing energy E(b) = 0.021 +/- 0.001 eV for the A and B excitons, and 0.0 23 +/- 0.001 eV for the C exciton in wurtzite GaN within the framework of the effective mass approximation.