Surface emission of $InxGa1−xN$ epilayers under strong optical excitation

Effects of strong optical excitation on the properties of surface emission from an InGaN/GaN heterostructure grown by metal-organic chemical-vapor deposition have been investigated. An intriguing feature observed was that as the excitation intensity increased the surface emission spectrum evolved abruptly from a single dominating band to two dominating bands at a critical intensity. This phenomenon has a sharp phase transition or a switching character and can be accounted for by (i) the formation of an electron–hole plasma state in the InGaN vertical cavity under strong optical excitation, (ii) the photoreflectance effect (variation of index of refraction with excitation intensity), and (c) the Fabry–Pérot interference effect in the InGaN vertical cavity. These findings are expected to have impact on the design of the laser structures, in particular on the design of the vertical-cavity surface-emitting laser diodes based on III-nitride wide-band-gap semiconductors.