Bonding process using indium-silver alloy which can withstand high temperature was investigated at relatively low temperature. We used a thermal evaporator and vacuum coater for making indium-silver contact. From the result of experiment, we observed that indium and silver films which have good quality are formed. From phase diagram of In-Ag alloy, we can find that melting point of these compounds increases with the silver content, i.e. eutectic (144° C) <AgIn2 (166° C) < (300° C) < (670° C) < (695° C). And these compounds are determined by the composition ratio of the source metal. Now we confirmed the thermal characteristics of Indium-Silver alloy is controlled by silver. Consequently we have developed Ag/In/Ag multi-layer composite which has higher melting point than that of normal contact. The melting point of Ag/In/Ag multi-layer is about 700° C. The joint cross-sections are studied using SEM(scanning electron microscopy) and EDX(Energy Dispersive X-rays). From these data, we observed that the composition and microstructure of Ag/In/Ag multi-layer were reliable and this bonding procedure is a better technique compared to the conventional structure of quantum well LED and GaN/Si LED structure was made by using sapphire for substrate and might be good for high temperature electronic devices in the future.
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