Failure Analysis of InP-Based Edge-Emitting Buried Heterostructure Laser Diodes Degraded by Forward-Biased Electrostatic Discharge Tests

Abstract

We investigated the forward-biased electrostatic discharge (ESD)-induced degradation that is one of the important reliability issues for InPbased edge-emitting buried heterostructure laser diodes. Although it has been suggested that the degradation mechanism is related to optical damage, the detailed mechanism has not been established. Thus, we carried out failure analysis. Two elliptically shaped degraded regions, which were introduced by the first and second ESD pulses, were observed in an active layer. A peculiar chain-like degradation was created along the longitudinal axis. This degradation was caused by light absorption at an active layer. We also investigated the relationship between forward-biased ESD tolerance and an aging test. We observed a decrease in tolerance as a result of the aging test for laser diodes with cleaved facets. This decrease was sufficiently suppressed by facet coating. We identified two reasons why facet coating is important. One is to obtain sufficient ESD tolerance under initial conditions, and the other is to suppress the decrease in ESD tolerance during aging.

Electrostatic-discharge-induced degradation of 1.3μm AlGaInAs∕InP buried heterostructure laser diodes

“…Although the ESD tolerance of facet-uncoated FP LDs was 1.2 kV, that of facet-coated FP LDs was higher than 3 kV. 8 This difference was mainly caused by suppression of facet oxidation. We also found that ion cleaning of the facet just prior to coating influences the ESD tolerance.…”

“…[5][6][7] Forward-biased ESD-induced degradation is caused by melting of the active layer at the facet following optical absorption. 6,8 In contrast, reverse-biased ESD-induced degradation is caused by destruction of the p-n junction by the electric field. 7 Although these ESD-induced degradation mechanisms of GaInAsP / InP LDs have been clarified, those of AlGaInAs/ InP LDs remain uncertain.…”

“…We have previously found that the reverse current is a good measure of degradation in an ESD test. 7,8 Specifically, degradation was defined to have occurred when V r decreased by more than 0.5 V from its initial value. The cumulative degradation ratio as a function of the ESD test voltage is graphed in Fig.…”