Properties of phosphorus doped ZnO (original) (raw)
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Journal of Alloys and Compounds, 2018
To study the effects of implantation on ZnO thin films grown on Si substrates, we have subjected it to phosphorous ion implantation for 10, 40, and 70 s through plasma immersion ion implantation and rapid thermal annealing. Low-temperature photoluminescence spectra of the as-implanted samples exhibited a reduction in the donor-bound exciton peak at 3.36 eV with implantation time. The photoluminescence spectrum of the 70 s implanted 1000 C-annealed sample confirmed acceptor-type doping. X-ray diffraction measurements showed a reduction in the c-axis length along the <002> direction with implantation time, evidencing phosphorous-ion incorporation in the implanted films, which was further confirmed by the blue shifting of the E2 high peak in the Raman spectra. XPS measurements affirmed the presence of the P 2p peak, a signature of PeO bond, and confirmed the substitution of Zn atoms by P atoms and the subsequent formation of the Pzn-2Vzn complex essential for acceptor-type conductivity.
Electronic Structure of P-Doped ZnO Films with p-Type Conductivity
Journal of Nanoscience and Nanotechnology, 2006
The electronic structure of laser-deposited P-doped ZnO films was investigated by X-ray absorption near-edge structure spectroscopy (XANES) at the O K -, Zn K -, and Zn L 3 -edges. While the O K -edge XANES spectrum of the n-type P-doped ZnO demonstrates that the density of unoccupied states, primarily O 2p-P 3sp hybridized states, is significantly high, the O K -edge XANES spectrum of the p-type P-doped ZnO shows a sharp decrease in intensity of the corresponding feature indicating that P replaces O sites in the ZnO lattice, and thereby generating P O . This produces holes to maintain charge neutrality that are responsible for the p-type behavior of P-doped ZnO. Both the Zn K -, and Zn L 3 -edge XANES spectra of the P-doped ZnO reveal that Zn plays no significant role in the p-type behavior of ZnO : P.
Growth of epitaxial p-type ZnO thin films by codoping of Ga and N
Applied Physics Letters, 2006
Codoping of Ga and N was utilized to realize p-type conduction in ZnO films using rf magnetron sputtering. The films obtained at 550°C on sapphire showed resistivity and hole concentrations of 38 ⍀ cm and 3.9ϫ 10 17 cm −3 , respectively. ZnO films also showed a p-type behavior on p-Si with better electrical properties. ZnO homojunctions synthesized by in situ deposition of Ga-N codoped p-ZnO layer on Ga doped n-ZnO layer showed clear p-n diode characteristics. Low temperature photoluminescence spectra of codoped films also revealed a dominant peak at 3.12 eV. The codoped films showed a dense columnar structure with a c-axis preferred orientation.
Journal of Applied Physics, 2014
Photoluminescence and secondary ion mass spectrometry investigation of unintentional doping in epitaxial germanium thin films grown on III-V compound by metal-organic chemical vapor deposition Influence of thermally diffused aluminum atoms from sapphire substrate on the properties of ZnO epilayers grown by metal-organic chemical vapor deposition J. Vac. Sci. Technol. A 29, 03A106 (2011); 10.1116/1.3549136 Microstructural compositional, and optical characterization of GaN grown by metal organic vapor phase epitaxy on ZnO epilayers Electrical and optical studies of metal organic chemical vapor deposition grown N-doped ZnO films
Journal of Crystal Growth, 2013
The authors report on the p-type conductivity in the ZnO films, grown on c-Al 2 O 3 substrates by molecular-beam epitaxy, using N and Te codoping and thermal annealing. In the electrical properties, the N and Te codoping effectively suppresses the background electron concentration of ZnO films, and the thermal annealing causes the conductivity conversion from n-type to p-type. In the structural properties, the N and Te codoping deteriorates the crystalline quality of ZnO films, even if Te doping contributes to improve the crystallinity, and the thermal annealing recovers the degraded crystalline quality again. In the optical properties, the N and Te codoping simultaneously increases the donorrelated emission, the acceptor-related emission, and the nonradiative recombination in ZnO films, while the thermal annealing relatively enhances the acceptor-related emission. It is proposed that (i) the N and Te codoping simultaneously induces N-related defects and donor-type defects along with free acceptors in the ZnO films, but the amount the N-related defects is larger than the donor-type defects and the free acceptors; and (ii) the thermal annealing relatively activates the N-related defects and suppresses the donor-type defects.
Properties of homoepitaxial ZnO and ZnO:P thin films grown by pulsed-laser deposition
Zinc Oxide Materials and Devices III, 2008
We have investigated the morphology, crystalline quality, the transport and electronic properties of homoepitaxial ZnO and ZnO:P thin films grown by pulsed-laser deposition. Atomic surface steps are visible for growth temperatures of 650°C and higher. The unit cell volume of undoped thin films is smaller than that of the hydrothermal substrates. Phosphorous doping increases the unit cell volume such that a perfect lattice match is achieved for a nominal phosphorous content of 0.01 wt.%. Undoped thin films have a net doping concentration below 10 15 cm -3 , whereas the phosphorous doping increases the free electron concentration at room temperature to 10 17 cm -3 and above. Temperature dependent Hall effect measurements show that interstitial zinc with a thermal activation energy of 34 meV is a dominant donor in homoepitaxial ZnO:P thin films. The Hall mobility of such samples is similar to ZnO single crystals grown by seeded chemical vapor transport. Low temperature photoluminescence measurements reveal recombination of free excitons and excitons bound to interstitial zinc and excitons bound to neutral and ionized aluminum donors. Defect related deep luminescence is not observed for undoped homoepitaxial thin films. In contrast phosphorous doping introduces two broad recombination bands centered at 2.9 eV and 1.9 eV.
Journal of Applied Physics, 2008
The transport properties of phosphorous-doped ZnO thin films, grown by pulsed-laser deposition on thermally pretreated hydrothermally grown ZnO single-crystal substrates, are reported. The ZnO:P thin films show very good morphological and structural properties as confirmed by atomic force microscopy (AFM), high resolution x-ray diffraction, and Rutherford backscattering (RBS) channeling. Steps of height c /2 are visible in AFM investigations for all samples. For an oxygen partial pressure of 0.1 mbar, two-dimensional growth was found. RBS channeling of a ZnO:P film shows a minimum yield of 0.034 which is comparable to that of an annealed substrate (0.033). Hall effect measurements revealed that all films are n-type for the present growth conditions. Peak mobilities of 800 cm2/Vs have been observed around 70 K, in line with the high structural quality of the samples. Room-temperature mobility in ZnO:P is up to 170 cm2/Vs.
Unexpected influence of substrate temperature on the properties of P-doped ZnO
Acta Materialia, 2008
The electrical conductivity of phosphorus-doped ZnO (P:ZnO) was found to change with sputter substrate temperature. Unexpectedly, n-type conductivity was obtained for samples deposited at substrate temperatures of 200, 250 and 300°C, but p-type conductivity was achieved for samples deposited at room temperature (RT). The type of a ZnO sample was determined and cross-checked by using three different techniques: the Hall effect, the Seebeck effect and magnetic field-dependent Hall voltage measurements. The n-type samples had conductivities of 11-45 S cm À1 and the p-type sample possessed a conductivity of 0.74 S cm À1. Furthermore, significantly different activation energies were found for the n-type (10 meV) and p-type (134 meV) P:ZnO samples, which were in good agreement with the positions of the donor and acceptor levels in the band structure reported in the literature. SIMS profiling measurement revealed that the oxygen concentration in the P:ZnO film deposited at RT was clearly higher than those in the films deposited at higher substrate temperatures. The results and relevant mechanisms were discussed. It appears that the n-type or p-type conductivity of a P:ZnO sample was determined mainly by the dominance of the n-type defect donors or the P induced acceptors.
Journal of Alloys and Compounds, 2011
ZnO thin films were deposited by ultrasonic spray technique, zinc acetate was used as starting solution with a molarity of 0.1 M. A set of indium (In) doped ZnO (between 2 and 8 wt%) thin films were grown on glass substrate at 350 • C. The present work is focused on the influence of the doping level on the structural, optical and electrical films properties. Optical film characterization was carried by using UV-visible transmission spectroscopy, the optical gap was deduced from absorption. From X ray diffraction (XRD) analysis, we have deduced that ZnO films are formed with nanocrystalline structure with preferential (0 0 2) orientation. The grain size is increased with In doping from 28 to 37 nm. Electrical characterization was achieved using two-probes coplanar structure, the measured conductivity varies from 2.3 to 5.9 cm −1 when increasing the doping level. However the optical gap is reduced from 3.4 to 3.1 eV.