Technical Papers and Presentations

A horizontal array of Si microlines (line width ~1 µm) was formed on a Silicon-on-Insulator (SOI) wafer [1] and was used as a photodetector to study the photoresponse in the wavelength range 400 nm to 1100 nm. The fabrication of partial suspended Si microstructure array was made using a novel technique that consists of various techniques consisting of plasma etching, electron beam lithography (EBL) and wet etching [2]. The device under the full illumination shows a peak Responsivity of 18 A/W at 800 nm, at a bias of 1V which is more than an order of magnitude of the Responsivity in a commercially available Si detector (≤ 1 A/W). The detector shows a response more than 10 A/W in a broad band of 400 nm to 1000 nm. Also by illuminating the different parts of single microline, the photocurrent from each part can be recorded. It has been found that such a high response is obtained because of partial suspension of microlines which has been validated through COMSOL Multiphysics® simulation. In COMSOL Multiphysics® simulation we mainly used the Semiconductor Module coupled with AC/D module in frequency domain. The partial suspension isolates each microline of the array from the bulk of the wafer and helps in the prevention of carrier recombination by the bottom SiO₂ layer and increases the carrier lifetime. As we decrease the width of the oxide layer and increase the extent of device suspension, there is a systematic increase in the photocurrent. The important quantity that causes this change is the net carrier recombination rate which decreases as we increase the suspension of Si microline interpreted from the surface plot of Figure 1, (see color bar).

References:

1. P. Duy Tran, J. Thomas Macdonald, B. Wolfrum, R. Stockmann, T. Nann, A. Offenhausser, and B. Thierry, Appl. Phys. Lett., 2014, 105, 231116
2. L. Pescini, A. Tilke, R. H. Blick, H. Lorenz, J. P. Kotthaus, W. Eberhardt and D. Kern, Nanotech., 1999, 10, 418-420