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Enhancing the External Quantum Efficiency of Porous Silicon LEDs Beyond 1 % by a Post-Anodization Electrochemical Oxidation

Published online by Cambridge University Press:  09 August 2011

B. Gelloz ,
T. Nakagawa  and
N. Koshida
B. Gelloz
Affiliation:
Division of Electronic and Information Engineering, Faculty of Technology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184 8588, Japan
T. Nakagawa
Affiliation:
Division of Electronic and Information Engineering, Faculty of Technology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184 8588, Japan
N. Koshida
Affiliation:
Division of Electronic and Information Engineering, Faculty of Technology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184 8588, Japan
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Abstract

External quantum efficiencies (EQEs) of electroluminescent devices based on porous silicon (PS) reported to date are still below the minimum requirements for practical applications such as display devices (1 %) and optical interconnection (10 %). Post-anodization anodic oxidation of PS to enhance the EQE of electroluminescence from devices based on a thin transparent indium tin oxide contact mounted on either porosified n+-type silicon or p+n+-type silicon has been investigated. Enhancement of EQE by more than 2 orders of magnitude has been achieved on our devices. CW EQE of 0.51% has been obtained by using a single anodically oxidized n+-type porous layer. The device based on the p+n+ substrate yielded a CW EQE of 1.1 %, with a power efficiency of 0.08%. It is the first time that EQE greater than 1% is obtained. Furthermore, anodically oxidized devices show better stability than non-oxidized devices. The anodic oxidation proceeds in such a way that it mainly decreases the size of nonconfined silicon in PS. The dramatic enhancement in EQE can therefore be explained by preferential reduction of leakage carrier flow through non-confined silicon.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 536: Symposium F – Microcrystalline & Nanocrystalline Semiconductors - 1998 , 1998 , 15
Copyright
Copyright © Materials Research Society 1999

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