ZnO/p-Si heterojunction photodiode by sol–gel deposition of nanostructure n-ZnO film on p-Si substrate

doi:10.1016/j.mssp.2010.05.005

Materials Science in Semiconductor Processing

Volume 13, Issue 3, September 2010, Pages 137-140

https://doi.org/10.1016/j.mssp.2010.05.005 Get rights and content

Abstract

The electrical and photovoltaic properties of the nanostructure ZnO/p-Si diode have been investigated. The nanostructure ZnO/p-Si diode was fabricated using sol–gel spin coating method. The ideality factor and barrier height of the diode were found to be 3.18 and 0.78 eV, respectively. The obtained n ideality factor is higher than 2, indicating that the diode exhibits a non-ideal behavior due to the oxide layer and the presence of surface states. The nanostructure of the ZnO improves the quality of ZnO/p-Si interface. The diode shows a photovoltaic behavior with a maximum open circuit voltage V_oc of 0.26 V and short-circuits current I_sc of 1.87×10⁻⁸ A under 100 mW/cm². It is evaluated that the nanostructure ZnO/p-Si diode is a photodiode with the obtained electronic parameters.

Introduction

In recent years, much research has been focused on semiconductor-based ultraviolet (UV) photodiodes. Photodiodes operating in the short wavelength UV region are important devices that can be used in various commercial and military applications. For example, visible–blind UV photodiodes can be used in space communications, ozone layer monitoring and flame detection. Currently, light detection in the UV spectral range still uses Si-based optical photodiodes.

Zinc-oxide (ZnO) films have been extensively studied for practical applications including bulk acoustic resonators [1], transparent conducting electrode materials for various electronic devices such as solar cells [2], electroluminescence devices [3], etc. Various techniques have been employed to obtain ZnO films. These include metalorganic chemical vapour deposition [4], molecular beam epitaxy [5], pulsed laser deposition [6], spray pyrolysis [7], [8] and sol–gel spin coating [9], [10]. Among these, the sol–gel process presents an easy way to integrate ZnO devices into the Si technology, since it offers the possibility of excellent compositional control, multicomponent oxide layers of many compositions on substrate, simplicity, homogeneity, lower crystallization temperature and low production costs.

ZnO-based UV photodetectors offer promising advantages in research and development due to ZnO's direct and wide band gap, strong UV-response, feasibility of simple and low cost processing and capability of working in harsh environments [4], [5], [6]. It is interesting that such a simple photodiode structure as the n-ZnO/p-Si has not been widely reported except by a small number of studies to date [11], [12], [13], [14], [15], [16].

In the present study, the nanostructure ZnO/p-Si photodiode was fabricated using the sol–gel spin coating method. The n-ZnO nanostructures directly were grown on p-type substrate. We have evaluated that this gives a high quality and well-defined interface between n-ZnO and p-Si. We report the first investigation of electrical properties of n-ZnO/p-Si photodiode fabricated by sol–gel spin coating method.

Section snippets

Experimental

ZnO film was deposited on silicon substrate using sol–gel spin coating method. The Si used in study was p-type (boron-doped) single crystal 〈100〉 with a thickness of 600 μm and a resistivity of 5–10 Ω-cm. Firstly, Si wafer was degreased through RCA cleaning procedure, i.e., a 10 min boiling in NH₄OH+H₂O₂+6 deionized (DI) (18 MΩ DI water), which was followed by a 10 min boiling in HCl+H₂O₂+6 DI. For ohmic contact, the high-purity aluminium (99.999%) with a thickness of 150 nm was thermally evaporated

Structural properties of the nanostructure ZnO film

Fig. 2 shows the XRD spectra of the nanostructure ZnO film. The analyses of XRD data reveal the peaks corresponding to the (1 0 0), (0 0 2), (1 0 1), (1 0 2), (1 1 0) and (1 0 3) planes of the hexagonal ZnO crystal structure. From these results, it can be observed that the films reveal the existence of a ZnO phase with a hexagonal wurtzite structure. XRD of the ZnO film shows a strong ZnO (0 0 2) diffraction peak centered at 34.379° with a full-width at half-maximum (FWHM) of 0.188°. The peak at around 70°

Conclusions

The electrical and photovoltaic properties of the nanostructure ZnO/p-Si diode have been investigated. The crystallite size of nanostructure ZnO film was determined by both the XRD result and SEM image. The ideality factor (3.18) and barrier height (0.78 eV) of the diode were determined and these values showed that the nanostructure of the ZnO has a significant effect on device performance. The obtained results showed that the nanostructure ZnO/p-Si diode was a photodiode with a maximum open

Acknowledgements

This work was supported by Anadolu University Commission of Scientific Research Projects under Grant no. 061039 and was partially supported by the National Boron Research Institute (BOREN) (Project Number: BOREN-2006-26-Ç25-19). One of authors wishes to thank BOREN.

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ZnO/p-Si heterojunction photodiode by sol–gel deposition of nanostructure n-ZnO film on p-Si substrate

Abstract

Introduction

Section snippets

Experimental

Structural properties of the nanostructure ZnO film

Conclusions

Acknowledgements

Applied Surface Science

Solar Energy Materials and Solar Cells

Current Applied Physics

Journal of Crystal Growth

Journal of Crystal Growth

Surface and Coatings Technology

Physica B

Solar Energy Materials and Solar Cells

Applied Surface Science

Microelectronics Journal