The crystallization of amorphous Si induced by Al during heat treatment has been investigated by cross section and plan view transmission electron microscopy. The lowest temperature of Al induced crystallization of amorphous Si was found to be 440 K. The crystallization temperature, however, depends on the thickness of Al layers in layered structures and on the concentration of Al in co-deposited layers below 1-nm-layer thickness and 15 at.% of Al concentration, respectively. Al-induced crystallization in layered structures starts at the Al/amorphous Si interfaces and is located close to them. The amount of crystallized Si depends on the quantity of Al and on the temperature and increases with them. The mechanism of crystallization involves intermixing of Al with Si and the formation of an alloy of high metal concentration in the amorphous/crystalline interface. When the formation of this alloy is not assured due to low Al concentration, then crystallization does not start or the process of crystallization stops. In Al induced crystallization the nucleation of polycrystalline Si grains rather than their crystal growth is affected.

Abstract-A fully integrated triplexer for multi-band ultrawideband radio is presented. The triplexer utilizes a microstrip network and three combined broadside-and edge-coupled filters. It is fully integrated in a printed circuit board with low requirements on the printed circuit board process tolerance. Three flat sub-bands in the frequency band 3.1-4.8 GHz have been achieved. The group delay variation within each 500 MHz sub-band was measured to be around 1 ns. A good agreement between simulation and measurement was obtained.

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