Degradation Mechanisms of Heterogeneous III-V/Silicon 1.55-μm DBR Laser Diodes

This paper reports an extensive analysis of the degradation processes of heterogeneous III-V/Silicon infrared laser diodes designed for integrated telecommunications and interconnects. By submitting the devices to a series of constant current stress tests, a gradual degradation of the main device parameters was observed. In particular, in every stress scenario the devices under test showed: 1) an increase in the threshold current; 2) a decrease of the turn-ON voltage; and 3) an increase in the apparent carrier concentration within the space charge region. The variation of the electrical parameters (turn-ON voltage and apparent charge concentration) was found to be significantly correlated to the optical degradation for long stress times; the results support the hypothesis that degradation originates from an increase in the non-radiative recombination rate, possibly due to the diffusion of defects toward the active region of the devices. In order to investigate the physical origin of those defects, a capacitance deep level transient spectroscopy analysis was performed. The results indicate the presence of five different deep levels, with a main trap located around 0.43 eV above the valence band energy. This trap is compatible with an interface defect located between the In(0.53)AlxGa(0.47-x)As separate confinement heterostructure region and the InP layer.