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The increasing demand for more advanced photonic integrated circuits has created the need to combine semiconductor materials with different lattice constants, i.e., GaAs on Si. During the past few years, much has been reported concerning the epitaxial lift-off technique. The most widely reported bonding method of epitaxial lift-off films is van der Waals bonding. However, there are problems with van der Waals-bonded devices. For instance, it has a long bonding time, which hinders an industrial use. Recently, we have investigated refinements of the epitaxial lift-off and grafting technique through using a single, transparent polymer membrane to support the material during the etch of a sacrificial layer, then depositing Au and Sn multilayers onto the lifted off devices and new host substrate. The devices are bonded by applying heat and pressure in a reducing atmosphere. The multilayer structures investigated in this work produce a resulting AuSn alloy with approximately 84 wt.% gold, but can be bonded with a peak temperature of 235 degree(s)C. In this paper we report our results in the optimization of the bonding parameters, with different diffusion barriers, new multilayer structures, as well as new applications of our bonding technique. We achieved important improvements in reliability and yield. The main advantages of our technology are thin bonding layers achieved with a minimum use of gold and an outstanding bonding quality reached in the large temperature range between 235 degree(s)C and 286 degree(s)C without flux. A thin, void free bonding layer means low thermal resistivity, which is especially important for laser diodes and high power devices. Further advantages of our new technique are the attainable precise control of the bonding layer thickness and the possible alignment of the devices through the transparent support and bonding membrane. We applied our new bonding technique to different optoelectronic devices such as MQWs and commercial laser bars and have simultaneously bonded a large number of devices. The bonded samples were investigated with several standard surface analysis techniques like optical microscopy, scanning electron microscopy and energy dispersive X-ray analysis as well as mechanical tests.
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