The influence various sources of fluctuation on the statistical parameters of the vertical cavity surface emitting lasers output radiation

Based on statistical modeling, a numerical analysis of the effects exerted by different factors (fluctuations of the spontaneous emission intensity, nonequilibrium carrier concentration, injection current density) on the statistical characteristics of radiation at the output of surface emitting semiconductor lasers in the region of polarization instability has been performed. In this region the effect of fluctuations is maximal, offering the possibility for substantiated conclusions about relative effects of the parameters. In a theory of semiconductor lasers it is thought that the intensity fluctuations of spontaneous emission represent the dominant source of fluctuations, whereas all other sources may be neglected. As demonstra ted by the results of conducted statistical modeling, this statement is too rigorous; moreover, such a source is not dominant. Taking into consideration fluctuations of the carrier concentration, which result in fluctuations of the amplification factor, we can derive a complete set of the relationships observed experimentally. This result cannot be associated with features our model because in our theory spontaneous emission is a significant factor. If the influence of spontaneous emission would be the dominant factor, it would affect the simulation results. The obtained data make it possible to doubt the key role of the spontaneous emission intensity fluctuations in the process of statistical characteristics formation for the output radiation and to take into account fluctuations of the nonequilibrium carrier concentration.

Effect of Electron Irradiation on Electrical and Electroluminescent Properties of n+p 4H-SiC Structures

A study of how electron irradiation affects the current-voltage (I-V) and electroluminescence (EL) characteristics of two types of 4H-SiC n+p structures with p-base and base doping to ~5∙1015 cm-3 is presented. The characteristics were measured prior to irradiation and after each of five stages of irradiation with 0.9 MeV electrons at doses in the range from 1∙1015 to 1.1∙1016 cm-2. The irradiation leads to an increase in the recombination current, decrease in the intensity of the edge EL (hνmax≈3.18 eV), and increase in the intensity of the infra-red (IR) EL (hνmax≈1.35 eV), which starts to predominate. Presumably, this indicates that the nonequilibrium carrier lifetime decreases and the concentration of acceptor type defects grows as a result of the irradiation. The IR EL, attributed to a complex defect containing a silicon vacancy, is of interest for development of single-photon sources of light.