Ž . Journal of Non-Crystalline Solids 227–230 1998 1354–1358 Amorphous silicon sensors for oxidised porous silicon optical waveguides buried in silicon wafers G. de Cesare a , G. Maiello b , G. Masini b , V. Bondarenko c , A. Ferrari a, ) a INFM Unita di Roma, Dipartimento di Ingegneria Elettronica, UniÕersita ‘La Sapienza’ di Roma, Via Eudossiana 18, 00184 Roma, Italy ` ` b Dipartimento di Ingegneria Elettronica, Terza UniÕersita degli Studi di Roma, Via della Vasca NaÕale 84, 00146 Roma, Italy ` c INFM Unita di Roma, BSUIR, P. BroÕki 6, 220027 Minsk, Belarus ` Abstract We have developed an original technology to fabricate channel waveguides on monocrystalline silicon wafers, consisting of selective anodization followed by thermal processing. The obtained oxidised porous silicon waveguides show waveguid- ing properties, moreover, due to the fabrication process, the waveguides are placed just under the surface of the silicon wafer. A hydrogenated amorphous silicon film has been grown on top of the waveguide by a low temperature process, then Ž . aluminum contacts have been formed by standard lithography. Different device structures photodiodes and photoresistors are presented. Currentrvoltage properties in the dark and under light excitation accompanied with capacitancervoltage measurements have been used to develop a band diagram model. q 1998 Elsevier Science B.V. All rights reserved. Keywords: Amorphous silicon; Porous silicon; Optical waveguides; Photosensors 1. Introduction In the last decade the bottleneck in electronics to decrease device feature size and increase speed is w x recognized in standard electrical interconnects 1,2 . Innovative interconnection technologies to overcome this bottleneck are needed. Optics was early indicated as a good possibility to wx overcome the problems inherent in electronics 3. Advantages include higher speed, lower losses, larger bandwidths and absence of electromagnetic interfer- ence. As a matter of fact, many efforts have been ) Corresponding author. Fax: q39-6 4742647; e-mail: ferrari@die.ing.uniromal.it. made in research to develop intra-board and inter- wx board optical interconnects 4 . Recently, important developments have been made on a smaller scale in optoelectronic integrated cir- Ž . cuits IC in which planar optical waveguides on a semiconductor substrate are employed as optical in- Ž terconnects between active devices lasers, detectors, . light-emitting diodes, etc. and also in passive de- w x vices such as splitters, filters and couplers 5–7 . We have introduced a method to confine visible light in monocrystalline silicon wafers by using dense ther- Ž . mally oxidised porous silicon waveguides OPSWG w x 8,9 . Silicon oxide obtained by thermal annealing of porous silicon shows suitable characteristics for opti- cal interconnect applications, such as lower losses w x and stronger confinement 10 . 0022-3093r98r$19.00 q 1998 Elsevier Science B.V. All rights reserved. Ž . PII: S0022-3093 98 00311-1