CL as a tool for device characterisation: the case of laser diode degradation

Abstract

Cathodoluminescence is a powerful technique for the characterization of semiconductors. Due to its high spatial resolution, it is emerging as a suitable method for the study of semiconductor devices. The reduced dimension of the devices and the multilayer structure of their active parts demand experimental means with high lateral resolution and probe depth tunability for characterising the different layers forming the device structure. Degradation is a crucial technological issue for high power devices. In particular, the failures of laser diodes are due to the formation of defects during the laser operation. Those defects can be imaged by cathodoluminescence; furthermore, its spectroscopic capabilities permit to go beyond the mere observation of the non-luminescent area morphology, allowing a better understanding of the physical mechanisms of degradation. We present herein an overview of the cathodoluminescence analysis of catastrophically degraded high power laser diodes, both single mode and multimode broad emitter lasers. The study of the defects responsible of the degradation is a step forward to establish models of degradation, necessary to improve the laser power and durability.