Abstract
ABSTRACT The effect of annealing temperature on the structural properties of Al-N codoped ZnO films were studied by X-ray diffraction, photoluminescence and Raman spectroscopy. ZnO films were deposited by sputtering technique on silicon substrates at 20 oC, Al-concentration was kept constant and N-flow was changed to 6, 12 and 15 sccm. A thermal treatment was performed by annealing the sample during 30 minutes at 300, 400, 500, 600 and 700 °C. Before annealing, Raman spectra shows two vibration modes located at 275 and 580 cm-1 associated to the nitrogen incorporation and the presence of point defects. Both Raman intensities of modes I275 and I580 decreases when the nitrogen flow increases from 6 to 12 and 15 sccm, which is originated by a decreasing interstitial defects density. The improving of the crystal quality was confirmed by x-ray diffraction and room temperature photoluminescence measurements. After annealing, in the Raman spectra it was observed that I275 increases as the temperature increase, reaches a maximum intensity between 500 and 600 °C, and decreases for higher temperatures. X-ray diffraction measurements show that after annealing the compressive stress decrease progressively as the annealing temperature increase. This study suggests that 275 Raman mode could be used to estimate the optimal thermal treatment in order to achieve p-doping ZnO.
Highlights
Zinc oxide (ZnO) is a semiconductor with special interest because it has a wide band gap (3.36 eV at 300K) and large exciton binding energy (60 meV), which can be widely used in the manufacture of optoelectronic devices such light-emitting diodes, laser diodes, photo-detectors, transparent electrodes, gas sensors and solar cells
Another feature of ZnO not favorable to the p-type doping is the presence of native defects such as interstitial and vacancies acting as an n-type doping, generating a phenomenon known as self-compensation [1,2,3]
We study the influence of annealing temperature on the structural properties of Al-N codoped ZnO films grown on Si (100) at 20 oC by X-ray diffraction, photoluminescence and Raman microscopy in order to get a best understanding of both the intrinsic defects and NO density behavior during the annealing process
Summary
Zinc oxide (ZnO) is a semiconductor with special interest because it has a wide band gap (3.36 eV at 300K) and large exciton binding energy (60 meV), which can be widely used in the manufacture of optoelectronic devices such light-emitting diodes, laser diodes, photo-detectors, transparent electrodes, gas sensors and solar cells. One of the big challenges is to control the p-type doping due to its high activation energy and the low solubility of acceptor dopants. Nitrogen is the doping elements frequently used in order to replace the oxygen atoms and increases the hole concentration. Another factor limiting the production of high levels of p-type doping is the low solubility of nitrogen originated by a weak bond N-Zn, which is broken at high growth temperatures (300 - 600 oC).
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