Achieving efficient light emission has been a goal of silicon photonics research for a considerable time. It is well known that ion implanted defects (point defect clusters, extended {311} defects and dislocations) can provide luminescent centres in silicon that result in sub-band gap emission at wavelengths characteristic of the defect type [1]. Recently, we demonstrated a working LED at a wavelength of 1.218 µm, where the active layer was composed of implantation-induced interstitial clusters (the so-called W-line) [2]. However, despite such demonstrations, optimisation studies, including attempts to understand the factors limiting luminescent intensity, are lacking.

In this study, PL measurements and TEM have been used to investigate ion implanted optically active defect centres (principally W-line and R-line) in silicon following thermal annealing. The presence of boron in p-type wafers of varying boron concentration dramatically reduces the luminescence of the interstitial-related W- and X-centres in the concentration range 10¹⁵-10¹⁸ cm^-3 and complete suppression occurs above 3.2×10¹⁸cm^-3. We have also used implanted, activated boron profiles to assist in understanding the reduced optical intensity. Our results indicate that competition between the formation of optically active silicon clusters and largely non-radiative boron clusters is the mechanism responsible for the dramatic intensity reduction. In contrast, phosphorus in n-type wafers does not reduce luminescence intensity significantly at moderate concentrations. Optimum conditions for W- and R-line emission are also investigated.

[1] S. Coffa et al, Appl. Phys. Lett. 76, 321 (2000).

[2] J. Bao et al, Optics Express 15, 6727 (2007).

Supakit Charnvanichborikarn, Department of Electronic Materials Engineering, Australian National University, Canberra, ACT 0200, Australia
Byron J Villis, Centre for Quantum Computer Technology, University of Melbourne, Victoria 3010, Australia
Brett C Johnson*, Centre for Quantum Computer Technology, University of Melbourne, Victoria 3010, Australia
Jenny Wong-Leung, Department of Electronic materials Engineering, Australian National University, Canberra, ACT 0200, Australia
Jeffrey C McCallum, Centre for Quantum Computer Technology, University of Melbourne, Victoria 3010, Australia
Jim S Williams, Department of Electronic Materials Engineering, Austrlian National University, Canberra, ACT 0200, Australia

*presenting author