n-ZnO Films Research Articles

Characteristics of ZnON films and heterojunction diodes with varying O:N ratios

Zinc Oxynitride (ZnOxNy) thin films display high mobilities and a considerable tunability of both the free electron concentration and optical band gap. The properties achievable for this material system makes ZnOxNy an intriguing n-type absorber candidate in silicon-based tandem solar cells. We have studied how the O:N ratio affect structural, optical and electrical properties of magnetron sputtered ZnOxNy thin films, as well the electrical behavior of ZnOxNy-Si pn heterojunction diodes. X-ray diffraction of the ZnOxNy films indicate either a Zn3N2-like structure or ZnO-like grains in combination with structural disorder. As the O:N ratio is increased, the optical band gap of ZnOxNy films increase from 1.1 to 1.9 eV. Hall effect measurements of the n-type ZnOxNy films show free electron concentrations varying with the O:N ratio, from 9.8×1017 to 1.5×1016 cm−3. Hall mobility up to 88 cm2/Vs is achieved. We observe the formation of pn heterojunction diodes between ZnOxNy-films and p-Si. The electrical characteristics of these diodes are shown to depend on the ZnOxNy anion composition. Current rectification of 3.7 orders of magnitude is achieved between -1 and 1 V at room temperature. However, the built in voltage extracted from capacitance–voltage measurements are higher than theory suggest, implying an influence of defects on the electrical characteristics.

The influence of light incidence on the bipolar switching in the two-terminal devices with n-ZnO and p-SrCu2O2 films

The influence of light incidence on the bipolar switching in the two-terminal devices with n-ZnO and p-SrCu2O2 films

ZnO Films Obtained by Reactive Magnetron Sputtering: Microstructure, Electrical, and Optical Characteristics

In this study, a technology producing undoped crystalline zinc oxide films with purposefully changed electrical resistance ρ = 3 × 10–4–1 × 107 Ω cm has been developed. The relationship between the electrical characteristics of ZnO layers and the parameters of their deposition has been studied, and the conditions for the formation of high-resistance i-ZnO and low-resistance n-ZnO films with specified values of electrical resistance have been determined. It has been established that the dominant factor determining the conductivity of ZnO films is a change in the concentration of free carriers, controlled by oxygen vacancies. To select the optimal conditions for the formation of highly transparent coatings with a given conductivity, the microstructure and spectral properties (edge absorption and transmission spectra in the transparency region) of n-ZnO films deposited by reactive magnetron sputtering of a zinc target in an argon atmosphere with oxygen (10% Ar, 90% O2) at a pressure of 5 × 10–3 Torr have been studied. It has been shown that the developed method for the discrete formation of ZnO films on amorphous substrates provides stoichiometric crystal structures with a high packing density and spatial orientation of crystallites in the [002] direction. Even in the case of n-ZnO films with ρ = 3 × 10–3 Ω cm, the microstructure causes a high transmittance of the coatings.

High-Performance Ultraviolet Light-Emitting Diodes Using n-ZnO/p-hBN/p-GaN Contact Heterojunctions.

Effective ultraviolet light-emitting diodes (LEDs) were fabricated by clamping the n-ZnO films on the top of p-hBN/p-GaN/sapphire substrates. An ultraviolet emission originating from ZnO was measured from the diode under a forward bias, the electroluminescence (EL) spectra of which show a peak wavelength of ∼376 nm with a narrow full-width at half maximum of ∼12 nm. Compared with the reference diode fabricated by directly growing n-ZnO on the p-hBN substrates using metal-organic chemical vapor deposition, the proposed diode showed a dramatic increment of the EL intensity; meanwhile, its emission onset lowered down considerably. The improved optical property of the proposed LED is mainly ascribed to suppressing the formation of the BNO-related layer at the n-ZnO/p-hBN interface. The present work provides a simple and feasible approach for developing advanced ZnO-based optoelectronic devices.

Investigation of the Optical and Electrical Properties of ITO/ZnO/CdS/CuO:Co/Ag Structure for Solar Cell

In this work, a new structure ITO/n‐ZnO/n‐CdS/p‐CuO:Co/Ag for solar cell was prepared on a glass/ITO substrate. The RF sputtering was used to deposit the window layer (n‐ZnO) at different time periods in order to reach various thickness of this film. The n‐CdS thin films were synthesized by sol‐gel technique to reduce the energy bands. The buffer layer (p‐CuO:Co) was sputtered at 200 W, under 30% of oxygen. Then, the electrode (Ag) with a thickness of 100 nm was deposited by thermal evaporation under a pressure of 10−5 mbar. The photovoltaic activity results obtained from this structure showed that the above method is more relevant to achieve such structure. The electrical properties of this structure were investigated using the current‐voltage (I‐V) and AC impedance complex measurements. The values of open circuit voltage (Voc), short‐circuit current (Jsc), and fill factor (FF) are 0.46 V, 4.1 mA cm−2, and 30%, respectively. The analysis of complex impedance measurements was very useful to investigate the electrical behavior of n‐ZnO/n‐CdS and n‐CdS/p‐CuO:Co interfaces. The impedance data are presented in the Nyquist and Bode plots at different thicknesses of the n‐ZnO films. An equivalent circuit was used to analyze and to fit the experimental data. The validity of these fitting results is further supported by the extrapolation and the deconvolution of both process of the diffusion and recombination processes at the n‐ZnO/n‐CdS and n‐CdS/p‐CuO:Co interfaces, respectively. Our finding could provide an efficient method for fabricating a new configuration for improving the efficiency of inorganic ZnO/CuO solar cells as well as a useful approach for the analysis of complex impedance measurements. Further works are in progress in order to better improve the conversion efficiency.

Facile approaches to prepare n-ZnO/(i-ZnO)/p-GaN heterojunction light-emitting diodes with white-light-electroluminescence

White-light-emitting diode (LED) with effective energy conservation and long service life could be employed in numerous applications. In this study, the high-performance n-ZnO films were first prepared via pulsed laser deposition on p-GaN substrates and then the n-ZnO/p-GaN heterojunction LED was fabricated. This LED exhibits blue and yellow light emission, and their emission intensities can be tuned by adjustment of the fabrication parameters (e.g. oxygen pressure) and/or by introduction of a semi-insulating i-ZnO layer to form a p-GaN/i-ZnO/n-ZnO heterojunction. Thus, a facile approach has been proposed for the preparation of white LED.

Ar flow-rate effect for low-resistivity Al/Ti/Al Ohmic contact to n-ZnO thin films

<p class="Abstract">The Ar flow rate effect on the electrical and optical properties of the sputtered Al-doped ZnO thins films were investigated. It was shown that a strong X-ray peak from (002) and (004) planes is dominant, suggesting that most grains have <em>c</em>-axis perpendicular to the substrate surface. The (002)-ZnO and (004)-ZnO peaks were measured at 2q = 34.12<sup>0</sup>, and 71.85<sup>0</sup>, respectively. It was also found that the growth rate of the Al-doped ZnO thin films increases when the sputtering power is increased. The transmittance of these film are strongly dependent on the sputtering power with the maximum transmittance of 92% was obtained at the sputtering power of 150 W and 50 sccm of Ar flow rate. The resistivity of the films is decreases as the Ar flow rate is increased. The lowest resistivity of 9.74 x 10<sup>-4</sup> W.cm was obtained at the films with Ar flow rate of 80 sccm. The mobility increases with the Ar flow rate increases. The carrier concentration also indicates the same pattern as the mobility. The transmittance of Al-doped ZnO thin films is also strongly dependent on the Ar flow rate. It was also observed the variation of contact resistivity of Al/Ti/Al to Al-doped n-ZnO thin films. The specific contact resistivity <em>r<sub>c</sub></em> of 1.8x10<sup>−5</sup> W.cm<sup>2</sup> was obtained at 150 nm-thick Al.</p>

See-through metal oxide frameworks for transparent photovoltaics and broadband photodetectors

In this work, we report metal-oxide based fast and stable transparent self-powered broadband (UV to NIR) photovoltaic devices. Using sputtering technique, we prepared the large-scale and transparent metal-oxide heterojunction device by formation of p-Cu-Cu2O/n-ZnO films on a FTO glass substrate. The heterojunction of Cu–Cu2O/ZnO is invisible to human eyes due to its high energy bandgap to render high transparency (>80%) for long wavelength light within the range 600–1100 nm. Meanwhile, it strongly absorbs short wavelength of UV light (below 400 nm), which may cause hurts to human eyes or skin cancers.The transparent Cu–Cu2O/ZnO device is the invisible electric power generator due to photovoltaic behaviour with the open-circuit-voltage of 0.36 V and high short-circuit-current value (1.83 mA), resulting in the maximum conversion efficiency of 0.405%. In addition, the transparent Cu–Cu2O/ZnO photovoltaic device also works as the self-operating photodetector. In the photovoltaic mode, Cu–Cu2O/ZnO heterojunction provided the fast and stable photoresponse (rise time ~3.89 ms and decay time ~4.12 ms) towards white light which is considered to be the fastest performance of Cu2O/ZnO based thin film photodetectors.These results represent a significant advancement in the see-through photovoltaic device with low-cost and evidently high efficiency. We may consider the transparent window as a power generator to provide electric energy on-demand sites, such as buildings, houses, or vehicles, while protected from the harmful UV radiation due to the smart functioning window.

The structure and the optical-electrical properties of the ZnO films and the Al:ZnO/N: ZnO homojunction photodiode

In this article, Al or N-doped ZnO films are prepared by wet chemical deposition method, and then the Al-ZnO/N-ZnO homojunction photodiode is structured. The influence of triethanolamine (TEA) content and deposition temperature on the structure, phase, and optical-electrical properties of N-ZnO films is investigated. The results of X-ray Diffraction (XRD) measurement show that the N-ZnO films have a hexagonal wurtzite structure with a preferred growth orientation along (002) crystal plane. The obvious Raman peak appeared at 436 cm−1 should be assigned to non-polar high-frequency E2H mode, which indicates the good crystallinity of N-ZnO film. The results of low temperature photoluminescence (LT-PL) measurement exhibit that the peak of UV emission, which shifts from 386 to 390 nm with the increase in measurement temperature from 50 to 250 K, may be mainly the exciton emission, coming from shallow donor Zni to valence band (Zni →VB: ΔE~3.15 eV) or conduction band to the shallow acceptor No (CB→No: ΔE~3.215 eV). Two visible emissions peaks may be attributed to the electron transitions from the single charged oxygen vacancies Vo+ and the double charged oxygen vacancies Vo++ defects, respectively. Three infrared emission peaks may be related to the electron transitions from the transition from deep donor level (Vo, Zni) to deep acceptor level (OZn) or the intra band transition between two states of Vo and Zni. For the response times of Al-ZnO/N-ZnO homojunction photodiode, the rise time (τr) is <2 ms and the decay time (τd) is about 22 ms. The value of responsivity (R) is calculated to be about 0.274 mA/W.

Photovoltaic property of n-ZnO/p-Si heterojunctions grown by pulsed laser deposition

Zinc oxide (ZnO) thin films were grown on p-Si substrates under various oxygen partial pressure (p(O2)) from 5.3 to 9.3 Pa by using pulsed laser deposition. In x-ray diffraction analysis, n-ZnO thin film grown under an p(O2) of 8 Pa showed the highest intensity of (002) diffraction peak and highly c-axis oriented. At room temperature, all the n-ZnO thin films grown at various p(O2) showed near band edge emissions about 385 nm, and the performance of n-ZnO/p-Si heterojunction grown at p(O2) of 8 Pa shows better than that of the heterojunction with n-ZnO layer grown at p(O2) of 5.3, 6.7, and 9.3 Pa. The performance of the heterojunction with and without Al-doped ZnO (AZO) layer was more improved by post-annealing at 200 °C, so that the heterojunction with and without AZO layer showed power conversion efficiency (PCE) of 0.61% and 1.5%, respectively. By measurement of external quantum efficiency (EQE), it was found that the improved PCE of the heterojunction with AZO layer was attributed to the overall enhanced EQE values from ultraviolet to near infrared.

Improvement in switching characteristics and long-term stability of Zn-O-N thin-film transistors by silicon doping

The effects of silicon doping on the properties of Zn-O-N (ZnON) films and on the device characteristics of ZnON thin-film transistors (TFTs) were investigated by co-sputtering silicon and zinc targets. Silicon doping was effective at decreasing the carrier concentration in ZnON films; therefore, the conductivity of the films can be controlled by the addition of a small amount of silicon. Doped silicon atoms also form bonds with nitrogen atoms, which suppresses nitrogen desorption from the films. Furthermore, Si-doped ZnON-TFTs are demonstrated to exhibit less negative threshold voltages, smaller subthreshold swings, and better long-term stability than non-doped ZnON-TFTs.

Fabrication of p-CuO/n-ZnO heterojunction diode via sol-gel spin coating technique

We report a facile all-solution approach for the growth of nanostructured p-CuO and n-ZnO thin films. The influence of annealing temperature on the physical properties of CuO and ZnO thin films was examined. XRD and Raman spectra depict the structural and phase purity of solution grown CuO and ZnO films. The electrical as well as the optical properties of thin films were also studied. The average optical transmission of CuO and ZnO thin films in the visible spectral region was found to be above 80 and 95% respectively. Band gap energy variations on annealing temperature were investigated for CuO as well as ZnO films. Surface morphology analyzed by FESEM shows that the films are very smooth. All solution grown p-n heterojunction using p-CuO and n-ZnO films was fabricated in the structure ITO/n-ZnO/p-CuO/Au which showed rectification behavior with a turn on voltage of 2.5V and an ideality factor of 3.15.

Hydrothermal growth of n-ZnO films on a patterned p-GaN epilayer and its application in heterojunction light-emitting diodes

The hydrothermal growth (HTG) of crystalline n-ZnO films on both the nonpatterned and patterned p-GaN epilayers with a honeycomb array of etched holes is demonstrated, and its application in n-ZnO/p-GaN heterojunction light-emitting diodes (HJ-LEDs) is reported. The results reveal that an HTG n-ZnO film on a patterned p-GaN layer exhibits a high-quality single crystal with FWHMs of 0.463 and 0.983° obtained from a ω-rocking curve and a ϕ-scan pattern, respectively, which are much better than those obtained on a nonpatterned p-GaN layer. In addition, the n-ZnO/patterned p-GaN HJ-LED exhibited a much better rectifying diode behavior owing to having a higher n-ZnO film crystallinity quality and an improved interface with the p-GaN layer. Strong violet and violet-blue lights emitted from the n-ZnO/patterned p-GaN HJ-LED at around 405, 412, and 430 nm were analyzed.

Characterization and device applications of p-type ZnO films prepared by thermal oxidation of sputter-deposited zinc oxynitride

Formation of nitrogen-doped p-type ZnO (p-ZnO) and related homojunction devices has been reported extensively using a variety of techniques with the exception of thermal oxidation of ZnON that is a simple and less explored method. We converted sputter-deposited ZnON films to p-ZnO at relatively low oxidation temperatures (400–500 °C) as compared with other reports. Chemical bonding states of nitrogen in p-ZnO films were examined by XPS analysis and the mechanism of p-type doping was discussed. Films were characterized by XRD, SEM, photocurrent spectroscopy, and photoluminescence (PL) measurement. Films were composed from nano-size crystallites with (100) preferential orientation. A shallow acceptor level with a 70–90 meV binding energy and a 1.72-eV deep level were measured and identified. PL thermal quenching of the films had activation energy of 34 meV. Schottky barrier (SB) and homojunction diodes, with two different types of n-ZnO, were fabricated on films and their parameters were compared with the reported data. The SB and both types of homojunction diodes had high rectification factors (104-105) and good device parameters. The conductance of homojunction diode based on sputter-deposited n-ZnO showed thermal activation energies of 0.08–0.12 eV, 0.16–0.20 eV, and 0.40–0.50 eV. The homojunction diode based on n-ZnO nano-rods exhibited strong electroluminescence in the visible region from which two defect-related transition energies of 2.21 eV and 2.66 eV were obtained. In conclusion, good quality p-ZnO films and related devices can be prepared by thermal oxidation of ZnON films.

The effects of active layer thickness and annealing conditions on the electrical performance of ZnON thin-film transistors

Thin-film transistors (TFTs) based on ZnON semiconductors were fabricated, and their electrical characteristics were evaluated with respect to the active layer thickness and annealing conditions. At a fixed annealing temperature, the electrical performance decreases with decreasing ZnON thickness. X-ray photoelectron spectroscopy (XPS) studies on the oxygen 1s peak of ZnON suggest that the diminished charge transport properties may be attributed to the formation of an oxygen rich capping layer with fixed thickness on top of the active layer upon heat treatment. Secondary ion mass spectrometry (SIMS) analyses show that indeed the top portion of ZnON films becomes rich in oxygen as the anneal temperature in air increases.The experimental results indicate that optimum field effect mobility and switching ability are achieved at an annealing temperature of 300 °C with a 20 nm-thick ZnON active layer. XPS analyses on the nitrogen 1s peak of ZnON films suggest that the portion of stoichiometric Zn3N2 is highest at this annealing temperature, which is anticipated to provide high conductivity paths to the free electrons. The devices were next subjected to negative bias illumination stress (NBIS), however the amount of ZnON TFT degradation does not exhibit any mobility dependence, unlike what is observed in devices incorporating conventional oxide semiconductors such as In-Ga-Zn-O (IGZO).

Relationship between the electrical properties of the n-oxide and p-Cu2O layers and the photovoltaic properties of Cu2O-based heterojunction solar cells

We investigated the relationship between the electrical properties (of the n-oxide semiconductor layer and the p-Cu2O sheet) and the obtainable photovoltaic properties of Al-doped ZnO (AZO)/n-oxide/p-Cu2O heterojunction solar cells that were fabricated using either p-type non-doped Cu2O or Na-doped Cu2O (Cu2O:Na) sheets (prepared by thermally oxidizing a Cu sheet) functioning as the active layer as well as the substrate. We fabricated some heterojunction solar cells using p-Cu2O (non-doped) sheets and n-ZnO thin films with various electron concentrations (N) in the range of 1017―1020cm−3; non-doped and Al- or Cu-doped ZnO thin films were deposited under various O2 or O3 gas atmosphere pressures using a pulsed laser deposition (PLD) method. The obtained photovoltaic properties exhibited a tendency to increase as N was increased from 1017 to about 3×1019cm−3; the values remained at these maximum levels as N was increased to about 8×1019cm−3, and then they decreased as N was increased further. With an N on the order of 1020cm−3, the reduction of photovoltaic properties was attributed to an increase in the discontinuity of the conduction band at the interface between the n-ZnO and p-Cu2O layers. In addition, we found that the hole concentration (P) in Cu2O:Na sheets (i.e., Cu2O sheets postannealed with various Na compounds) could be controlled in the range of 1014―1019cm−3 by varying the annealing temperature and duration. As another example, the obtained photovoltaic properties in heterojunction solar cells that were fabricated by depositing n-(Ga0.975Al0.025)2O3 thin films on p-Cu2O:Na sheets by PLD remained constant as P was increased to approximately 1×1016cm−3, and then they decreased significantly as P was increased further. The reduction of the obtained photovoltaic properties in heterojunction solar cells fabricated using Cu2O:Na sheets with a P above about 1.4×1016cm−3 was attributed mainly to decreases of both the depletion layer width and the diffusion length.

High-performance ultraviolet detection and visible-blind photodetector based on Cu2O/ZnO nanorods with poly-(N-vinylcarbazole) intermediate layer

This study reports a high-performance hybrid ultraviolet (UV) photodetector with visible-blind sensitivity fabricated by inserting a poly-(N-vinylcarbazole) (PVK) intermediate layer between low-cost processed Cu2O film and ZnO nanorods (NRs). The PVK layer acts as an electron-blocking/hole-transporting layer between the n-ZnO and p-Cu2O films. The Cu2O/PVK/ZnO NR photodetector exhibited a responsivity of 13.28 A/W at 360 nm, a high detectivity of 1.03 × 1013 Jones at a low bias of −0.1 V under a low UV light intensity of 24.9 μW/cm2. The photo-to-dark current ratios of the photodetector with and without the PVK intermediate layer at a bias of −0.5 V are 1.34 × 102 and 3.99, respectively. The UV-to-visible rejection ratios (R360 nm/R450 nm) are 350 and 1.735, respectively. Several features are demonstrated: (a) UV photo-generated holes at the ZnO NRs can effectively be transported through the PVK layer to the p-Cu2O layer; (b) the insertion of a PVK buffer layer significantly minimizes the reverse-bias leakage current, which leads to a larger amplification of the photocurrent; and (c) the PVK buffer layer greatly improves the UV-to-visible responsivity ratio, allowing the device to achieve high UV detection sensitivity at a low bias voltage using a very low light intensity.

Structural, optical, electrical properties, and strain/stress of electrochemically deposited highly doped ZnO layers and nanostructured ZnO antireflective coatings for cost-effective photovoltaic device technology

High quality polycrystalline and nanostructured ZnO thin films were electrochemically deposited from aqueous solution of zinc nitrate (Zn(NO3)2) at negative electrochemical potential (EC=−0.6 to ‑−1.4V) and moderate temperature (75–80°C) on various substrates (Cu, Si, Mo/glass, ZnSe/Mo/glass, F:SnO2/glass). Undoped (i-ZnO) films were grown free of strain on Cu and Mo/glass using intermediate lattice matched buffer (ZnSe). The i-ZnO films on Si exhibited high tensile in-plane stress of σ=4GPa. Growth rates depended on substrate orientation and electrochemical potential varying from EC=−1.1V for deposition on Si(100) to EC=‑−1.3V for optimum deposition on Si(111). Growth rates of undoped and doped (n-ZnO) films with Al and In dopant (Al:ZnO, In:ZnO) on Mo/glass depended on the solute dopant (AlCl3, InCl3) concentration (0.2nm/s for i-ZnO, 0.7nm/s for n-ZnO with n=5mM, 1.2nm/s for n-ZnO with n=9mM). Hydrostatic compressive strains by incorporation of 0.4–12.0 at.% Al were in the range of εh=‑−0.070 to ‑−2.000. The resistivity of metal-pin contacted n-ZnO/i-ZnO films (Me/Al:ZnO/i-ZnO/Mo/glass, Me/In:ZnO/i-ZnO/ZnSe/Mo/glass, Me: Au/Ni) was in the order 105Ω·cm. In the UV–VIS-NIR region (1.5–5.0eV), the reflectivity of the films did not exceed 20% and the (optical) band gap of Eg=3.5eV indicated their high optical quality and material purity. The optical properties of electrochemically grown ZnO nanorod arrays (transparency: 70-80% at 1.5-3.0eV and band-gap: 3.3–3.7eV) were additionally analyzed by photoreflectance spectroscopy. By application of optical modulation techniques, both spectrally (4meV at 300K) and spatially (7meV/cm) resolved gap energies were quantified and the role of nitric (HNO3) and nitrate (NH4NO3) additives was extensively reinforced. Antireflective coatings (ARCs) of ZnO nanorods assembled in Cu(In,Ga)Se2 thin film solar cells were found to quench the surface reflectivity by 5% at least. Integration of electrochemically processed transparent conductive ZnO films and ZnO ARCs in solar cell device technology is anticipated to provide key-solutions for cost effective energy harvesting.

Slanted n-ZnO nanorod arrays/p-GaN light-emitting diodes with strong ultraviolet emissions

Both of oblique angle deposition and conventional deposition techniques were used by a RF sputtering system to grow the slanted (β = 32°) and planar (β = 0°) n-ZnO films on p-GaN, respectively. These two kinds of n-ZnO/p-GaN heterojunctions were then fabricated the light-emitting diodes (LEDs). The electrical and optical properties of these two kinds of LEDs were investigated systematically. The results show that the slanted n-ZnO/p-GaN LEDs have a lower turn-on voltage and less leakage current than that of planar n-ZnO/p-GaN LEDs. Moreover, different from the planar n-ZnO/p-GaN LEDs which emitting colors changes with injection current, the slanted n-ZnO/p-GaN LEDs retains UV emissions (385-400 nm) under the entire range of injection currents we applied. The dominant UV luminescence of slanted n-ZnO/p-GaN LEDs is attributed to the ZnO near band edge transitions, indicating the high quality of slanted ZnO films and exhibiting the essential property dedicated to nano-sized heterojunctions. Hence, we have demonstrated that the slanted n-ZnO/p-GaN LEDs fabricated by oblique angle deposition have better performance than the planar n-ZnO/p-GaN LEDs fabricated by convention deposition means.

Influence of growth temperature and post-annealing on an n-ZnO/p-GaN heterojunction diode

We report on an n-ZnO/p-GaN heterojunction diode fabricated from zinc oxide (ZnO) films at various growth temperatures (450, 500, 550, and 600 °C) by RF sputtering. The films were subsequently annealed at 700 °C in N2 ambient. To investigate the influence of the growth temperature of n-ZnO films, the microstructural, optical, and electrical properties were measured using scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL), and Hall measurements. The XRD pattern showed the preferred orientation along the c-axis (002) regardless of growth temperature. The PL spectra showed a dominant sharp near-band-edge (NBE) emission. Current–voltage (I–V) curves showed excellent rectification behavior. The turn-on voltage of the diode was observed to be 3.2 V for the films produced at 500 °C. The ideality factor of ZnO film was observed to be 1.37, which showed the best performance of the diode.