Coughlan, C., Mirza, M. M.A. , Kirdoda, J. , Dumas, D., Smith, C., McCarthy, C. , Mowbray, H., Watson, S. , Millar, R. and Paul, D. J. (2023) Variation of Sidewall Passivation on Sub-um Selectively Grown Ge-on-Si Devices Towards Single Photon Avalanche Detectors. In: SPIE OPTO 2023, San Francisco, CA, USA, 28 Jan-3 Feb 2023, 124170M. ISBN 9781510659391 (doi: 10.1117/12.2665493)
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Abstract
Developing single photon avalanche diodes (SPADs) at short-wave infrared (SWIR) wavelengths beyond 1000 nm has attracted interest lately. Numerous quantum technology applications such as light detection and ranging (LIDAR), imaging through obscurants and quantum communications require sensitivity in this region. In quantum communications, operation at the telecoms wavelengths of 1310 nm and 1550 nm is essential. Ge-on-Si SPADs offer potential for lower afterpulsing and higher single photon detection efficiencies in the SWIR in comparison with InGaAs/InP SPADs, at a lower cost due to Si foundry compatibility. In this study, Ge-on-Si devices are fabricated on silicon-on-insulator (SOI) substrates, with a separate absorption, charge and multiplication layer (SACM) geometry and a lateral Si multiplication region. This Si foundry compatible process will allow for future integration with Si waveguides and optical fibres. The Ge is selectively grown inside sub-μm wide SiO2 trenches, reducing the threading dislocation in comparison with bulk Ge; a typical process for integrated Ge detectors. Here we deliberately exposed Ge sidewalls with an etch-back technique, to allow a passivation comparison not normally carried out in selectively grown devices planarised by chemical-mechanical polishing. Reduced dark currents are demonstrated using thermal GeO2 passivation in comparison to plasma-enhanced chemical-vapourdeposition SiO2. The improved passivation performance of GeO2 is verified by activation energy extraction and density of interface trap (Dit) calculations obtained from temperature-dependent capacitance-voltage (CV) and conductance-voltage (GV) measurements. This highlights the benefit of optimal surface passivation on sub-μm wide selectively grown Ge-on-SOI photodetector devices, potentially critical for waveguide integrated SPADs.
| Item Type: | Conference Proceedings |
|---|---|
| Additional Information: | The author would like to acknowledge the supported of the following grants: UK EPSRC EP/L016753/1, EP/S026428/1, EP/T001011/1, EP/T00097X/1, Innovate UK (44835), Royal Academy of Engineering (RF- 201819-18-187, CiET2021 123). |
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | McCarthy, Charlie and Mirza, Dr Muhammad M A and Watson, Dr Scott and Mowbray, Miss Hannah and Coughlan, Mr Conor and Paul, Professor Douglas and Millar, Dr Ross and Dumas, Dr Derek and Smith, Charlie and Kirdoda, Mr Jaroslaw |
| Authors: | Coughlan, C., Mirza, M. M.A., Kirdoda, J., Dumas, D., Smith, C., McCarthy, C., Mowbray, H., Watson, S., Millar, R., and Paul, D. J. |
| College/School: | College of Science and Engineering > School of Engineering College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering |
| ISSN: | 0277-786X |
| ISBN: | 9781510659391 |
| Copyright Holders: | Copyright © 2023 SPIE |
| Publisher Policy: | Reproduced in accordance with the copyright policy of the publisher |
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