Properties of a pn junction developed with a Si microprobe by vapour-liquid-solid growth using in situ doping

This paper reports the development of a pn junction by growing n-type Si-microprobe arrays on a p-layered Si (111) substrate by Au-catalyzed vapour-liquid-solid (VLS) growth at 700 degrees C using the mixed gas of Si2H6 and PH3. The diameter of the probes was selectively controlled in the range of 1 - 5 mu m by patterning Au dots with the desired size and thickness, whereas the length is dictated by the growth conditions and time. The growth rate, impurity concentration and resistivity of these probes were observed to vary with the gas ratio of PH3 to Si2H6. The pn junction formed at the interface of the n-probe and p-layer of the substrate exhibits standard diode characteristics with the built-in potential around 0.7 V and the reverse breakdown at about -11 V. This needle-like pn junction array may be applied as insertion electrodes, photodetectors, photosensitive emitter array devices, etc. Also low-temperature realization of a Si microprobe would be compatible to process this junction array with on-chip circuitry to develop smart chips for sensor applications.