Efficient silicon light emitting diodes made by dislocation engineering
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Efficient silicon light emitting diodes made by dislocation engineering M. A. Lourençoa, R. M. Gwilliama, G. Shaob and K.P. Homewooda a School of Electronics, Computing and Mathematics, bSchool of Engineering, University of Surrey, Guildford, Surrey, GU2 7XH, United Kingdom
ABSTRACT
Efficient room temperature silicon based light emitting diodes have been fabricated by conventional ULSI processes using a recently developed dislocation engineering approach. Strong silicon band edge luminescence was observed from devices fabricated by low energy boron implantation into silicon substrates followed by high temperature rapid thermal annealing. In this paper we review the luminescence properties of silicon light emitting diodes and give an example of how this approach can be employed to fabricate and optimise light emitting devices operating at different wavelengths.
INTRODUCTION
Despite of great efforts over the past decade to obtain technologically viable and efficient light emission from silicon, such as erbium in silicon [1], silicon/germanium [2] and iron disilicide [3], none has so far been applied commercially. The reasons for this are a combination of the lack of genuine or perceived compatibility with conventional ULSI technology and also the high thermal quenching giving poor room temperature efficiencies. For example, for the FeSi2 system, electroluminescence (EL) at 80 K from ion beam synthesised has been observed on devices fabricated at low iron doses [4]. However, strong thermal quenching was reported on these devices, leading to a poor performance or a complete absence of the EL at room temperature. Dislocation engineering is a recently developed method used, primarily, to fabricate efficient silicon based room temperature light emitting devices [5]. This approach makes use of the controlled introduction of dislocation loops into silicon substrates by conventional ion implantation and thermal processes. The dislocation loops introduce a local strain field, which modifies the band structure and provides spatial confinement of the charge carriers, thus allowing strong intrinsic silicon band-edge luminescence to be observed at room temperature. To minimise the number of process steps, boron implantation was used both to introduce the dislocation loop array and as the p-type dopant to form a p-n junction in an n-type silicon substrate. However, another implant species such as the host silicon could be employed to form the dislocations so that the dislocation engineering and subsequent doping to form the p-n junction can be achieved independently. Room temperature electroluminesecence with efficiency greater than 2 × 104 have been achieved, and device lifetime was found to be ~ 18 µs. The luminescence emission was found to vary on the process conditions; the influence of the sample fabrication details on the device characteristics has been reported elsewhere [6]. Nevertheless, no F5.1.1 Downloaded from https://www.cambridge.org/core. HKUST Library, on 13 Jun 2018 at 12:58:27, subject to the Cambridge Core te
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