Formation and Transient Photovoltaic Properties of ZnO/Si …
321
of photogenerated carriers at the additional recombination centers formed at this
interface.
5 Conclusions
In summary, the structural and electro-physical characteristics of ZnO/Si heterostructures formed by the magnetron film deposition from aluminum-doped ZnO target
are addressed. The film recrystallization and microcrystal structure restoration are
observed. It is found that the ZnO/Si barrier is about 0.66 eV and depends on the
annealing temperature of the implanted structures. Diode structures with a transparent electrode (ITO/ZnO/Si/Al) have photosensitivity in the wide spectral region
of 0.4–2.5 μm. The photosensitivity mechanisms in different spectral bands require
further refinement.
The deposited ZnO films with thicknesses of less than ≈70 nm have roughly three
times greater photovoltage magnitude compared with that having greater thicknesses,
and this coincide with the microstructural evolution of the film. The SPV decays slow
down accordingly exhibiting decay times of the order 10 μs at the small film thicknesses and 100 μs at the ones exceeding ≈70 nm. These results can be interpreted in
terms of the recombination and carrier trapping centers in the film and at the ZnO/Si
boundary, whose concentration varies with the film thickness.
It is furthermore shown that forming p-NiO/n-ZnO/Si heterostructure increases
the photovoltage magnitude, which is up to several times, and shortens the SPV
decays. This can be effectively used in manufacturing rapid photosensitive elements.
References
1. Pearton SJ, Norton DP, Ip K, Heo YW, Steiner T (2005) Recent progress in processing and
properties of ZnO. Prog Mater Sci 50(3):293–340
2. Bedia Z, Bedia A, Kherbouche D, Benyoucef B (2013) Electrical properties of ZnO/p-Si
heterojunction for solar cell application. Int J Mater Eng 3:59–65
3. Purica M, Budianu E, Rusu E (2000) Heterojunction with ZnO polycrystalline thin films for
optoelectronic devices applications. Microelectr Eng 51–52:425–431
4. Zheng ZQ, Yao JD, Wang B, Yang GW (2015) Light-controlling, flexible and transparent
ethanol gas sensor based on ZnO nanoparticles for wearable devices. Sci Rep 5:11070
5. Shih CC, Lee WY, Chiu YC, Hsu HW, Chang HC, Liu CL, Chen WC (2016) Transistor memory
devices using nano-floating gate of polymer/ZnO nanocomposites. Sci Rep 6:20129
6. Umit O, Daniel H, Hadis M (2010) ZnO devices and applications: a review of current status
and future prospects. Proc IEEE 98(7):1255–1268
7. Battaglia C, de Nicolás SM, Wolf SD, Yin X, Zheng M, Ballif C, Javey A (2014) Silicon
heterojunction solar cell with passivated hole selective MoO x contact. Appl Phys Lett
104:113902
8. Islam R, Shine G, Saraswat KC (2014) Schottky barrier height reduction for holes by Fermi
level depinning using metal/nickel oxide/silicon contacts. Appl Phys Lett 105:182103
321
of photogenerated carriers at the additional recombination centers formed at this
interface.
5 Conclusions
In summary, the structural and electro-physical characteristics of ZnO/Si heterostructures formed by the magnetron film deposition from aluminum-doped ZnO target
are addressed. The film recrystallization and microcrystal structure restoration are
observed. It is found that the ZnO/Si barrier is about 0.66 eV and depends on the
annealing temperature of the implanted structures. Diode structures with a transparent electrode (ITO/ZnO/Si/Al) have photosensitivity in the wide spectral region
of 0.4–2.5 μm. The photosensitivity mechanisms in different spectral bands require
further refinement.
The deposited ZnO films with thicknesses of less than ≈70 nm have roughly three
times greater photovoltage magnitude compared with that having greater thicknesses,
and this coincide with the microstructural evolution of the film. The SPV decays slow
down accordingly exhibiting decay times of the order 10 μs at the small film thicknesses and 100 μs at the ones exceeding ≈70 nm. These results can be interpreted in
terms of the recombination and carrier trapping centers in the film and at the ZnO/Si
boundary, whose concentration varies with the film thickness.
It is furthermore shown that forming p-NiO/n-ZnO/Si heterostructure increases
the photovoltage magnitude, which is up to several times, and shortens the SPV
decays. This can be effectively used in manufacturing rapid photosensitive elements.
References
1. Pearton SJ, Norton DP, Ip K, Heo YW, Steiner T (2005) Recent progress in processing and
properties of ZnO. Prog Mater Sci 50(3):293–340
2. Bedia Z, Bedia A, Kherbouche D, Benyoucef B (2013) Electrical properties of ZnO/p-Si
heterojunction for solar cell application. Int J Mater Eng 3:59–65
3. Purica M, Budianu E, Rusu E (2000) Heterojunction with ZnO polycrystalline thin films for
optoelectronic devices applications. Microelectr Eng 51–52:425–431
4. Zheng ZQ, Yao JD, Wang B, Yang GW (2015) Light-controlling, flexible and transparent
ethanol gas sensor based on ZnO nanoparticles for wearable devices. Sci Rep 5:11070
5. Shih CC, Lee WY, Chiu YC, Hsu HW, Chang HC, Liu CL, Chen WC (2016) Transistor memory
devices using nano-floating gate of polymer/ZnO nanocomposites. Sci Rep 6:20129
6. Umit O, Daniel H, Hadis M (2010) ZnO devices and applications: a review of current status
and future prospects. Proc IEEE 98(7):1255–1268
7. Battaglia C, de Nicolás SM, Wolf SD, Yin X, Zheng M, Ballif C, Javey A (2014) Silicon
heterojunction solar cell with passivated hole selective MoO x contact. Appl Phys Lett
104:113902
8. Islam R, Shine G, Saraswat KC (2014) Schottky barrier height reduction for holes by Fermi
level depinning using metal/nickel oxide/silicon contacts. Appl Phys Lett 105:182103