Temperature dependence of threshold current - A better criterion than T₀ ?

Experimental measurements of threshold current density as a function of temperature have been analysed in terms of the characteristic temperature, T0, and temperature gradient Del TJth = partial Jth/ partial T, for a number of semiconductor laser device structures. These include AlInGaAs/InP, InGaAsP/InP, and AlGaAs/GaAs. A theoretical model is used to investigate the possible loss mechanisms in laser diodes that cause the superlinear increase of threshold current with temperature. The characteristic temperature T0 is found to vary with temperature and device length, thus making it somewhat misleading when quoted without qualification. A different approach based on plotting In( Del TJth) vs. In(Jth) shows a linear relationship that is dependent on device structure only, allowing the use of a new figure of merit for the temperature performance of semiconductor lasers.