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Photoluminescence at room temperature of liquid-phase crystallized silicon on glass
The room temperature photoluminescence (PL) spectrum due band-to-band recombination in an only 8 μm thick liquid-phase crystallized silicon on glass solar cell absorber is measured over 3 orders of magnitude with a thin 400 μm thick optical fiber directly coupled to the spectrometer. High PL signal is achieved by the possibility to capture the PL spectrum very near to the silicon surface. The spectra measured within microcrystals of the absorber present the same features as spectra of crystalline silicon wafers without showing defect luminescence indicating the high electronic material quality of the liquid-phase multi-crystalline layer after hydrogen plasma treatment.
Scalable, high power line focus diode laser for crystallizing of silicon thin films
We present the design and performance of a diode laser module producing a high intensity line focus at 808 nm for material processing. The design is based on a linear array of 7 laser bars and beam forming optics featuring a micro-optic homogenizer. The module delivers a total output power of 900 W at 140 A and peak intensity created in the focus area of 10.3 kW/cm2. Two systems with line length of 5 cm and 10 cm at a large working distance of 110 mm have been realized. The chosen concept allows scaling in length by joining multiple modules which is of interest for material processing in industrial applications. Application results from laser crystallization of amorphous silicon seed layers used in the fabrication of photovoltaic cells for solar panels are given.
Process flow to integrate nanostructures on silicon grass in surface micromachined systems
The process flow to integrate metallic nanostructures in surface micromachining processes is presented. The nanostructures are generated by evaporation of microstructured silicon grass with metal. The process flow is based on the lift-off of a thin amorphous silicon layer deposited using a CVD process. All steps feature a low temperature load beneath 120 °C and high compatibility with many materials as only well-established chemicals are used. As a result metallic nanostructures usable for optical applications can be generated as part of multilayered microsystems fabricated in surface micromachining.