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A Led Based on Porous Polycrystalline Silicon

Published online by Cambridge University Press:  10 February 2011

W. N. Huang ,
K. Y. Tong  and
P. W. Chan
W. N. Huang
Affiliation:
Department of Electronic Engineering, Hong Kong Polytechnic University
K. Y. Tong
Affiliation:
Department of Electronic Engineering, Hong Kong Polytechnic University
P. W. Chan
Affiliation:
Department of Applied Physics, Hong Kong Polytechnic University
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Abstract

Previous studies on electroluminescence in porous silicon were based on crystalline wafers. In this paper, we shall report the characteristics of a LED based on porous effects in a cast polycrystalline silicon substrate. A layer of porous region was first formed on a cast polycrystalline silicon substrate by anodization, followed by the deposition of a semitransparent Au layer. Under forward bias, the LED emits stable yellowish white light (with the presence of bright spots) for currents above 20 mA/cm2. From the electroluminescence spectra measured, we suggest that the emission is due to the recombination of electron-hole pairs in a microplasma region. We propose a model where the microplasma is present in the depletion region of the heterojunction formed between the bulk polysilicon and the surface porous polysilicon. The defects and grain boundaries in a polycrystalline material facilitate the formation of such microplasma. The heterojunction model will also be used to explain the current characteristics of the LED. The effect on the LED characteristics due to indium coating on the porous substrate prior to Au deposition was studied, and the results agree with the heterojunction model. Our work shows that cast polycrystalline silicon substrates have potential for LED fabrication in cheap and large area applications.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 486: Symposium H – Materials & Devices for Silicon Based Optoelectronics , 1997 , 163
Copyright
Copyright © Materials Research Society 1998

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