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The function of a 60-nm-thick AlN buffer layer in n-ZnO/AlN/p-Si(111).

Wang W, Chen C, Zhang G, Wang T, Wu H, Liu Y, Liu C - Nanoscale Res Lett (2015)

Bottom Line: Meanwhile, the ZnO crystalline quality was significantly improved as verified by both XRD and PL analyses.The valence band offsets have been determined to be 3.06, 2.95, and 0.83 eV for ZnO/Si, ZnO/AlN, and AlN/Si heterojunctions, respectively, and the band alignment of ZnO/Si heterojunction was modified to be 0.72 eV after introducing the AlN buffer layer.Our work offered a potential way to fabricate Si-based ultraviolet light-emitting diodes and improve the device performances.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, and School of Physics and Technology, Wuhan University, Wuhan, 430072 People's Republic of China.

ABSTRACT
ZnO films were prepared on p-Si (111) substrates by using atomic layer deposition. High-resolution x-ray diffraction (XRD), scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and I-V measurements were carried out to characterize structural, electrical, and optical properties. After introducing a 60-nm-thick AlN buffer layer, the growth direction of the ZnO films was changed from [10] to [0002]. Meanwhile, the ZnO crystalline quality was significantly improved as verified by both XRD and PL analyses. It has been demonstrated that the reverse leakage current was greatly reduced with the AlN buffer layer. The valence band offsets have been determined to be 3.06, 2.95, and 0.83 eV for ZnO/Si, ZnO/AlN, and AlN/Si heterojunctions, respectively, and the band alignment of ZnO/Si heterojunction was modified to be 0.72 eV after introducing the AlN buffer layer. Our work offered a potential way to fabricate Si-based ultraviolet light-emitting diodes and improve the device performances.

No MeSH data available.


Related in: MedlinePlus

The room temperature PL spectra of samples a (without AlN) and b (with AlN). The inset shows the logarithmic intensity spectra.
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Fig3: The room temperature PL spectra of samples a (without AlN) and b (with AlN). The inset shows the logarithmic intensity spectra.

Mentions: The room temperature PL spectra of ZnO thin films with and without the AlN buffer layer are shown in Figure 3. The main PL peaks at about 380 nm were due to the free excitation emission in ZnO, and a low energy shoulder (at wavelength of 395 nm) was attributable to the emission related to point defects [24]. Usually, the ratio of band-edge transition (BET) to deep level emissions (DLEs) could evaluate the quality of ZnO films. It has been shown that the quality of ZnO films has been significantly improved after inserting the AlN buffer layer, because the ratio of BET to DLE of sample B (59.8) was larger than that of sample A (43.4). The DLE around 500 nm was caused by different intrinsic defects in ZnO films such as oxygen vacancies and zinc interstitials [14]. The very weak DLEs of samples A and B suggest that few zinc interstitials and few oxygen vacancies exist in the ZnO films, which can be attributed to the growth mechanism of ALD. The self-limiting aspect of ALD leads to a conformal deposition, because the precursors can adsorb and subsequently desorb from the surface where the reaction has reached completion, and then proceed to react with other unreacted surface areas, while the redundant former precursor should be cleaned by the purge process. In this way, the two reactions (ZnOH* and Zn(CH2CH3) in this work) proceeded in a sequential fashion to deposit a thin film with atomic level control [25].Figure 3


The function of a 60-nm-thick AlN buffer layer in n-ZnO/AlN/p-Si(111).

Wang W, Chen C, Zhang G, Wang T, Wu H, Liu Y, Liu C - Nanoscale Res Lett (2015)

The room temperature PL spectra of samples a (without AlN) and b (with AlN). The inset shows the logarithmic intensity spectra.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385121&req=5

Fig3: The room temperature PL spectra of samples a (without AlN) and b (with AlN). The inset shows the logarithmic intensity spectra.
Mentions: The room temperature PL spectra of ZnO thin films with and without the AlN buffer layer are shown in Figure 3. The main PL peaks at about 380 nm were due to the free excitation emission in ZnO, and a low energy shoulder (at wavelength of 395 nm) was attributable to the emission related to point defects [24]. Usually, the ratio of band-edge transition (BET) to deep level emissions (DLEs) could evaluate the quality of ZnO films. It has been shown that the quality of ZnO films has been significantly improved after inserting the AlN buffer layer, because the ratio of BET to DLE of sample B (59.8) was larger than that of sample A (43.4). The DLE around 500 nm was caused by different intrinsic defects in ZnO films such as oxygen vacancies and zinc interstitials [14]. The very weak DLEs of samples A and B suggest that few zinc interstitials and few oxygen vacancies exist in the ZnO films, which can be attributed to the growth mechanism of ALD. The self-limiting aspect of ALD leads to a conformal deposition, because the precursors can adsorb and subsequently desorb from the surface where the reaction has reached completion, and then proceed to react with other unreacted surface areas, while the redundant former precursor should be cleaned by the purge process. In this way, the two reactions (ZnOH* and Zn(CH2CH3) in this work) proceeded in a sequential fashion to deposit a thin film with atomic level control [25].Figure 3

Bottom Line: Meanwhile, the ZnO crystalline quality was significantly improved as verified by both XRD and PL analyses.The valence band offsets have been determined to be 3.06, 2.95, and 0.83 eV for ZnO/Si, ZnO/AlN, and AlN/Si heterojunctions, respectively, and the band alignment of ZnO/Si heterojunction was modified to be 0.72 eV after introducing the AlN buffer layer.Our work offered a potential way to fabricate Si-based ultraviolet light-emitting diodes and improve the device performances.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, and School of Physics and Technology, Wuhan University, Wuhan, 430072 People's Republic of China.

ABSTRACT
ZnO films were prepared on p-Si (111) substrates by using atomic layer deposition. High-resolution x-ray diffraction (XRD), scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and I-V measurements were carried out to characterize structural, electrical, and optical properties. After introducing a 60-nm-thick AlN buffer layer, the growth direction of the ZnO films was changed from [10] to [0002]. Meanwhile, the ZnO crystalline quality was significantly improved as verified by both XRD and PL analyses. It has been demonstrated that the reverse leakage current was greatly reduced with the AlN buffer layer. The valence band offsets have been determined to be 3.06, 2.95, and 0.83 eV for ZnO/Si, ZnO/AlN, and AlN/Si heterojunctions, respectively, and the band alignment of ZnO/Si heterojunction was modified to be 0.72 eV after introducing the AlN buffer layer. Our work offered a potential way to fabricate Si-based ultraviolet light-emitting diodes and improve the device performances.

No MeSH data available.


Related in: MedlinePlus