Photonics studies on dilute nitrides at long wavelength for telecommunication

Abstract

By adding a little nitrogen in InGaAs / GaAs quantum well (QW), a strong bandgap-bowing in the QW is caused. However, the incorporation of nitrogen results in lower photonuminescence intensity and wider line width as a result of increased non-radiative centers. In order to increase the efficiency of radiative recombination and hence reduce the laser threshold, a post-growth heat treatment has to be applied. Such kind of heat treatment results in a big blue shift due to interdiffusion and other effects. During growth, in order to incorporate nitrogen into InGaAs, the growth temperature is much lower than normal InGaAs growth. Large number of point defects is induced under such low temperature. This is the main cause of the interdiffusion at the interfaces of InGaAsN / GaAs QW. There are some other facts to cause the blue shift during heat treatment, such as local neighbourhood redistribution called short range ordered. In our study, different blue shift behaviors were clearly observed due to different blue shift mechanism. Post-growth heat treatment also affects the laser performance dramatically. Lower temperature treatment mainly decreases the absorption loss and higher temperature treatment improves the conductivity of the cladding layers. Different heat treatment also results in very different burn-in behavior. An optimized heat treatment will be concluded after the annealing discussion on laser devices. In order to assure longer emission wavelength well as higher emission efficiency, many efforts have been tried and will be discussed in this paper.