Investigation of ZnO/Si structural, electrical and optical properties prepared by sputtering and PLD

Skriniarova, Jaroslava; Kovac, Jaroslav; Bruncko, Jaroslav; Vincze, Andrej; Vesely, Marian; Novotny, Ivan; Janos, Lubomir; Jakabovic, Jan; Hasko, Daniel; Hasko, Daniel; Vincze, Andrej Slovakia

Zinc oxide (ZnO) is emerging as a multifunctional material for broad applications, such as ultraviolet detectors, Schottky diodes, acoustic wave devices in wireless communications because of its direct band gap of 3.37 eV at 300K. Compared with other wide band gap materials, ZnO has a larger exciton binding energy (59 meV), which assures more efficient excitonic emission at higher temperatures. However, the development of optoelectronic devices has been impeded by the fact that p-n homo-junctions in ZnO have been extremely difficult to fabricate.
The present contribution is based on study of polycrystalline ZnO films deposited by RF sputtering in Ar/N2 atmosphere and by pulsed laser deposition (PLD) on p-type and n-type Si, respectively. The structural, electrical and optical properties of processed devices were investigated before and after annealing in temperature range of 400-500 °C. The films deposited by RF sputtering show high resistivity ZnO n-type layer. After annealing in N2 atmosphere the conductivity of ZnO layer changed while ZnO/Si interface exhibits diffusion of Si into ZnO. This effect was confirmed by SIMS depth profile measurements. PLD deposited ZnO films under defined growth conditions (400°C) in O2 atmosphere show p-type layer formation. Rectifying and photoelectric behavior were investigated for p-Si / ZnO structures after thermal annealing.

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