1Department of Post Graduate Studies and Research in Physics and Electronics, Rani Durgavati University, Jabalpur –482001 (India).
2Gyan Ganga Institute of Technology and Sciences, Jabalpur.
The threshold current density for lasing in double hetero-structure GaAs lasers is known to be temperature dependence. At low temperature up-to approximately at 300K, threshold current density (Jth) is fairly constant. Above 1000K, Jth for laser operation increases rapidly with increasing temperature. The temperature dependence of Jth is usually described by a simple empirical formula Jth = J0 exp (T/T0) where, T0 and J0 are empirical parameters. In practice, measured T0 values are in the range 100–2500K depending on the actual configuration. A number of studies were recently reported on comparing computed and measured threshold current density behavior as a function of temperature. The most advanced use a drift-diffusion model for evaluating leakage current and a gain model in order to find the carrier density needed to achieve threshold at a certain temperature. There is a strong dependence on the injected level in the quantum well at threshold. The first level lies relatively high above the band edge. Thus the quasi-Fermi level is forced to be higher than in bulk material, in order to achieve the same gain, especially for high losses, when high carrier densities are needed. The analysis reveals that as the temperature decreases, the reduction in electron momentum increases the effectiveness of the acceptor ions as traps. It is likely that the recombination in the optical trap layer becomes much larger than recombination in the active region. As the temperature increases, maximum gain of the spectrum is shifted to a long-wavelength region. Thus, the higher the temperature, the lower the value of the gain, at which threshold lasing condition is fulfilled. Gallium arsenide lasers emit radiation in the near infrared portion of the spectrum. The exact wavelength depends on the temperature at which the laser is operated.
