Near-infrared sensitive photodiode

Near infrared sensitive photodiodes were developed by depositing hydrogenated microcrystalline SiGe alloys at low temperature by plasma enhanced chemical vapour deposition (PECVD).

Microcrystalline silicon germanium (µc-SiGe:H) is a low bandgap material whose optical and electrical properties are highly dependent on deposition conditions. Within the framework of a collaborative project with ST Microelectronics aimed at developing infrared sensitive photodiodes using a low thermal budget approach, INL developed and optimised all the microcrystalline materials (n- or p-doped µc-Si, µc-SiGe) by plasma assisted CVD (PECVD) deposition. N-I-P structures were then entirely produced within NanoLyon facilities, in a monolithic approach, with the active deposition being carried out in succession in the same reactor. Photodiodes could be made with an ITO / µc-Si:P / µc-Si1-xGex:H / µc-Si:B / Ag stack, without lithography, and allowing to obtain internal quantum yields higher than 80% in the visible range, and up to 20% in the near IR. A fraction of 60% Ge is optimal for a 200 nm thick intrinsic µc-SiGe:H absorption layer, combining satisfactory absorption and transport properties.


PhD contract ANRT-CIFRE 2019/1645 INL/ ST Microelectronics (Crolles)


Erwann Fourmond, Alestair Wilson


A. Wilson, E. Fourmond, B. Saidi, J.-G. Mattei, B. Fornacciari, et M. Gros-Jean, « Potential of hydrogenated microcrystalline silicon-germanium for low thermal budget near infrared sensors », in Physics and Simulation of Optoelectronic Devices XXXI, San Francisco, United States, mars 2023, p. 12. doi: 10.1117/12.2647554.

Cross section of a Si/Sige p-i-n photodiode for infra-red sensing
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