Temperature dependence of external differential quantum efficiency of GaN-based blue laser diode

The external differential quantum efficiency, defined as the ratio of number of photons emitted per unit time to number of carriers passing the laser diode junction, is known to be sensitive to laser diode’s operating temperature. In this paper, high-resolution spectral emissions of a commercially available GaN-based blue laser diode are measured and utilized to study the effect of temperature on the external differential quantum efficiency and over the operating temperature range of 270 – 330 °K. Upon studying the L-I curves and over the full range of laser diode’s operating current and temperature, three distinct temperature regimes of the quantum efficiency were identified with the regime of temperature range 285 -301 °K yielding the highest temperature stability. In addition to experimentally determining the characteristic temperature of the laser diode, the effect of non-radiative recombination and free carrier absorption processes on external differential quantum efficiency will be discussed.