NiSi(C) Schottky diodes for IR detection
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Un-cooled bolometer arrays have been considered as good choices for detection of infrared waves in the ranges of 3-5μm (MWIR: mid wavelength infrared) and 8-12μm (LWIR: long wavelength infrared). Advantages are found in their relative simplicity of mechanism and design, hence, fabrication cost, when compared to detectors working based on photon detection mechanisms. A temperature dependent resistor (or thermistor) is the core element of a bolometer. The rate of resistance dependency to temperature is a figure-of-merit for thermistor material, acting as the active element in a bolometer. This property is characterized by temperature coefficient of resistance (TCR). At the same time, for the better IR detection and imaging quality, high signal-to-noise ratio (SNR) is also sought. Different materials have been proposed and/or implemented commercially to work as thermistor materials. Among them are VOx, amorphous silicon, amorphous and poly SiGe.
A material structure that has been shown to be promising to act as IR detector is metal-silicide/silicon Schottky barrier . In this work, Schottky barrier chips, with pixel sizes ranging from 25μm 2 to 200μm2 are fabricated and analyzed. Schottky barriers are formed on lowly boron-doped silicon layer by NiSi. The boron concentration in Si varied from 1x1016 to 5x1017 cm-3. Furthermore, carbon is introduced to the structures to change the barrier height of Schottky. The detectors were characterized by TCR and noise measurements, using probe station and spectrum analyzer. Comparison of TCRs at 1 V bias voltage shows significant improvement of TCR by increase of boron concentration from 1x1016 to 5x1017 cm-3 (in absence of carbon). The highest TCR value of 4.47%/K is achieved for these samples for 25×25 μm2 pixel size. Incorporation of carbon to the B-doped Si layers improves TCR, as compared to lowly boron-doped carbon-free samples and TCR values of 4.55%/K is achieved. These data indicate the structure profile of the Schottky has a direct influence on the performance of the detectors.
Place, publisher, year, edition, pages
2012. , 34 p.
Engineering and Technology
IdentifiersURN: urn:nbn:se:kth:diva-108169OAI: oai:DiVA.org:kth-108169DiVA: diva2:579233
Master of Science - Nanotechnology
Hammar, Mattias, Professor