The detection limit of infrared thermographic investigations can be improved down to 10 µK by using a highly sensitive high-speed infrared camera in an online averaging lock-in thermography system. Together with a microscope objective, this allows lock-in thermography to be used as a simple and sensitive technique to localize the sites of leakage currents and other heat sources in electronic components. The practical realization of a novel lock-in thermography system is described and both test measurements and practical applications are introduced. The detection limit for surface-near local heat sources in silicon is a few microwatts with a spatial resolution down to 5 µm. Leakage sites in several microelectronic structures are imaged and assigned to the layout of the integrated circuit by comparing direct images with lock-in ones. The direct comparison of an averaged and background-subtracted stationary thermogram with a lock-in one, both measured under similar conditions at the same sample, clearly demonstrates the gain in information obtained by using lock-in thermography

Interfacial characteristics of Ga0.51In0.49P/GaAs heterostructures grown by metal-organic vapor-phase epitaxy in the temperature range from 600 °C to 730 °C were studied. Photoluminescence (PL) measurements have been used for this purpose. A PL peak with an energy of about 1.425 eV (870 nm) was continuously observed in samples containing the GaInP-to-GaAs interface. Excitation power dependent PL measurements show that this peak belongs to an excitonic recombination. Furthermore, a strong blue-shift of this PL-peak energy was observed as the excitation power increased. We attribute the 870 nm peak to the radiative recombination of spatially separated electron-hole pairs and suggest the type-II band alignment at the ordered GaInP to GaAs heterointerface under growth conditions reported here. Further investigations using x-ray diffraction measurements and simulations with dynamical theory show that the lower and upper interfaces are not equivalent. This explains the absence of type-II transition in most GaAs-to-GaInP lower interfaces.

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Photoluminescence analysis of Ga0.51In0.49P/GaAs single-quantum well structures grown by metal-organic vapor-phase epitaxy in the temperature range from 570 to 720 °C have been carried out. Besides the GaAs band-edge emissions, all SQW samples studied here exhibit a dominant long-wavelength peak, which is attributed to the spatially indirect transition due to the type-II band alignment of Ga0.51In0.49P/GaAs heterojunctions. The energy of the type-II PL emission has been found to depend strongly on the growth temperature indicating the strong influence of the growth temperature on the band alignment. The shifts of the type-II PL emission have been used to estimate the growth temperature dependent conduction and valence band discontinuity of the Ga0.51In0.49P/GaAs heterojunction. X-ray diffraction measurements and simulations using the dynamical theory were carried out to study the influence of the growth temperature on the unintended interfacial layers.