Photovoltaic and Electroluminescent Properties of Stain-Etched Porous Silicon Based Heterojunctions
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PHOTOVOLTAIC AND ELECTROLUMINESCENT PROPERTIES OF STAINETCHED POROUS SILICON BASED HETEROJUNCTIONS D. Dimova-Malinovska*, M. Tzolov*, M. Kamenova*, N. Tzenov*, M. Sendova-Vassileva*, D.Nesheva** *Central Laboratory for Solar Energy and New Energy Sources, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria, [email protected] **Institute of Solid State Physics, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria, ABSTRACT The results of photoelectric properties and electroluminescent studies of structures ZnO/porous Si/p-type c-Si/Al and ZnO/porous Si/p-n c-Si junction/Al are presented. Porous Si is prepared by stain etching of c-Si covered with thin Al film. The transparent ZnO film allows light emission through the top surface of the device under forward electrical bias. Photocurrent is observed under reverse bias and a photovoltaic effect is measured on the p-n junction PS device. The model based on injection of minority carriers through a narrow energy barrier into the porous Si and the presence of the barrier at the interface porous Si/c-Si is suggested for describing the electrical, photoelectric and luminescent properties of the structures. INTRODUCTION Soon after the observation of room-temperature photoluminescence (PL) from porous Si (PS) [1] it was demonstrated that this new material exhibits not only electroluminescence (EL) [2] but photoconductivity [3] and photovoltaic properties [4,5] as well. Although many studies of the optical, structural and electrical properties of PS have been carried out the light emission and transport mechanisms of PS are still under debate. Additionally, the low EL efficiency of lightemitting PS devices and the weak photovoltaic effect in PS structures require further work to achieve efficient photo- and optoelectronic devices. Mainly two methods have been applied for preparation of PS - electrochemical (ECE) [1] and chemical (stain) etching [6]. The method of PS fabrication by stain etching (SE) offers some advantages. It is easily accessible and gives the possibility to prepare very thin (
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