Micro-photoluminescence for the visualisation of defects, stress and temperature profiles in high-power III–Vʹs devices

Different applications of the micro-photoluminescence (μ-PL) mapping technique to the evaluation of semiconductor devices are described in this paper, based on detailed analyses of the PL spectral line-shape. The applications covered are connected to the general field of reliability investigations for III–V semiconductor high-power devices, like GaAs-based microwave transistors or laser diode arrays. Derived from a study of the local PL peak-shifts, whose origin can be thermal or mechanical, two types of application of the technique are shown: (a) local temperature maps on either individual devices or circuits under operation; and (b) local mechanical stress maps in high-power laser diode arrays, in relation to the packaging process for these devices. The most remarkable feature in these studies is the spatial resolution reached (in the range of 1 μm), together with the fact that the technique is non-invasive and does not require any specific preparation of the samples/devices to be investigated. Typical outputs are evaluations of the impact of the technology chosen (either at the level of the semiconductor chip itself or for the packaging solution) in terms of lifetime limitation, or else valuable experimental data for the validation of models used for the design of such devices.