A specific problem in failure analysis of InGaAs/ AlGaAs laser diodes asked for a deprocessing tool able to selectively etch gold from a Ti/Pt/Au triple metal layer. Attempts made by the usual I2/KI etch confirmed the damage that it causes to the crystal stack, and non-uniform attack of gold. A new etch, indicated as Epta-Methyl-bis-diodine, has been successfully employed. Careful time control and detailed characterization of the complex metallization pattern of the devices allowed not only to properly expose the Pt layer, but also to preserve the overall electrical connection, thus maintaining the capability of both measuring the electrical characteristics at low current injection and collecting the EBIC signal from the etched device.

The occurrence of sudden failures has been reported for 980 nm SL SQW InGaAs pump lasers. The post-mortem analysis reveals failure modes that are consistent with the formation of defects at the active area. The problem calls for two separate efforts: monitoring the degradation at suitable time resolution and structural characterization of defects. This article reports about the optical power and overall voltage monitoring results during a constant current lifetest, in which "sudden failures" switched off the lasers in a few hours, after 1500 hours of regular life, and about their interpretation based on TEM cross-sectional images across an EBIC-detected high recombination site. The hypothesis that Recombination Enhanced Defect Reaction (REDR) is a suitable mechanism for defect growth in forward biased GaAs-based diodes is proposed and discussed that REDR is the origin of the observed sudden failures, starting from native defects located in "cool" regions.

This article explores the intrinsic significance of EBIC maps, looking at the specific case of ridge laser structures, but starting from a much more general approach: the Reciprocity Theorem for Charge Collection first exploited by Donolato in 1985. It provides information on non destructive testing for structural analysis and defect detection in double heterostructure ridge lasers answering the questions about the significance of EBIC maps. Taking full advantage of both direct EBIC theory and Reciprocity Theorem, most of the observed features of EBIC images are analyzed. It can be concluded that any EBIC detected defect indicates an active scattering and recombination point for minority carriers in operating conditions: no uneffective defects may be claimed; and non isotropic comas may not be read as broadening of a stronger defect kernel: they are related to real defect extension.