Optical, electrical and thermal analysis for GaN semiconductor lasers

Device characteristics of GaN‐based semiconductor lasers have been analysed by numerical calculation. Anti‐guide‐like behaviour of the waveguide mode appears in InGaN laser structures where the cladding layers have insufficient thickness. Such phenomena are peculiar to laser structures with GaN material systems. The layer structure should be designed so as to suppress the anti‐guide mode. Carrier overflow is also a significant problem for GaN lasers. A high acceptor concentration for the p‐type cladding layer and the reduction of the active layer volume have a large effect on the reduction of such carrier overflow. In regard to the temperature characteristics, one of the restricting factors is the use of sapphire substrates which have relatively high thermal resistivity. The maximum operation temperature has been calculated based on the analysis for the thermal resistance of the device. It was shown that reduction in the stripe width as well as reduction in threshold current density and operation voltage is very important for improving the temperature characteristics of GaN semiconductor lasers.