Non-radiative current in InGaAs/AlGaAs laser diodes as a measure of facet stability

We present a novel, non-destructive optoelectronic technique to study passivation and degradation mechanisms at diode laser facets. We extract the non-radiative current components, I-nr, from the electroluminescence power-voltage-current characteristics. In InGaAs/AlGaAs (lambda = 0.98 mu m) laser diodes these currents have been identified as being primarily related to surface recombination, which increases during facet degradation. and can he decreased by a sulphur treatment. An analysis of the logarithmic change of I-nr with facet degradation or passivation shows a typical maximum or minimum respectively, which can be interpreted as a change in charge and density of a certain surface state. This technique permits relaxation processes to be analyzed quantitatively. (C) 1998 Elsevier Science Ltd. All rights reserved.