ELSEVIER Solar Energy Materials and Solar Cells 46 (1997) 261-269 Solar Energy Materials and Solar Cells Electrical and optical characterization of crystalline silicon/porous silicon heterojunctions C. Palsule a'*, S. Liu a, S. Gangopadhyay a, M. Holtz a, D. Lamp a, M. Kristiansen b "Department of Physics, Texas Tech University, Lubbock, TX 79409, USA b Department of Electrical Engineering, Texas Tech University, Lubbock, TX 79409 USA Received 31 May 1996; received in revised form 17 October 1996 Abstract We have investigated the photovoltage and photocurrent spectra of crystalline sili- con/porous silicon heterojunctions. The porous silicon layers were prepared using anodic etching of p-type crystalline silicon at a current density of 25 mA/cm 2. From the spectral dependence of the photovoltage and photocurrent, we suggest that the photovoltaic properties of the j unction are dominated by absorption in crystalline silicon only. We have also studied the effect of increase in the thickness of porous silicon layers on these spectra. We find that the open-circuit voltage of the devices increases, but the short-circuit current decreases with an increase in the thickness of the porous silicon layers. We propose a qualitative explanation for this trend, based on the increase in the series and the shunt resistance of these devices. The effect of hydrogen passivation on the junction properties by exposing the devices to hydrogen plasma is also reported. Keywords: Photovoltage spectra; Photocurrent spectra; Crystalline silicon/porous silicon het- erojunctions 1. Introduction and background The visible light emission from porous silicon (PS) [1] has generated a great deal of interest due to its potential technological applications. This has stimulated * Correspondence address. Hewlett-Packard, Integrated Circuits Business Division, Corvallis, OR 97330, USA. 0927-0248/97/$17.00 © 1997 Elsevier Science B.V. All rights reserved Pll S0927-0248(97)00004-4