Improved stability of black silicon detectors using aluminum oxide surface passivation

Juha Heinonen, Antti Haarahiltunen, Heikki Kettunen, Jukka Jaatinen, Mikko Rossi, Jouni Heino, Hele Savin, Mikko Juntunen

Research output: Contribution to journalConference articleScientificpeer-review

1 Citation (Scopus)
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We have studied how high-energy electron irradiation (12 MeV, total dose 66 krad(Si)) and long term humidity exposure (75%, 75 ˚C, 500 hours) influence the induced junction black silicon or planar photodiode characteristics. In our case, the induced junction is formed using n-type silicon and atomic-layer deposited aluminum oxide (Al2O3), which contains a large negative fixed charge. We compare the results with corresponding planar pn-junction detectors passivated with either with silicon dioxide (SiO2) or Al2O3. The results show that the induced junction detectors remain stable as their responsivity remains nearly unaffected during the electron beam irradiation. On the other hand, the SiO2 passivated counterparts that included conventional pn-junction degrade heavily, which is seen as strongly reduced UV response. Similarly, after humidity test the response of the induced junction detector remains unaffected, while the pn-junction detectors passivated with SiO2 degrade significantly, for instance, the response at 200 nm reduces to 50% from the original value. Interestingly, the pn-junction detectors passivated with Al2O3 exhibit no degradation of UV response, indicating that the surface passivation properties of Al2O3 are more stable than SiO2 under the studied conditions. This phenomenon is further confirmed with PC1D simulations suggesting that the UV degradation results from increased surface recombination velocity. To conclude, the results presented here suggest that black silicon photodiodes containing Al2O3-based induced junction are highly promising alternatives for applications that require the best performance and long-term stability under ionizing and humid conditions.
Original languageEnglish
Article number118520T
Pages (from-to)118520T
Number of pages7
JournalSPIE Conference Proceedings
Publication statusPublished - 11 Jun 2021
MoE publication typeA4 Article in a conference publication
EventInternational Conference on Space Optics - Online, Antiber Juan-le-Pins, France
Duration: 19 Oct 202023 Oct 2020


  • black silicon
  • photodiode
  • irradiation
  • humidity


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