Effect of Al Concentration on Structural, Optical and Electrical Properties of (Gd, Al) Co-Doped ZnO and Its n-ZnO/p-Si (1 0 0) Heterojunction Structures Prepared via Co-Sputtering Method

Abstract

Heterojunction structures of n-ZnO/p-Si were prepared through the growth of undoped ZnO and (Gd, Al) co-doped ZnO films onto p-type Si (1 0 0) substrates, using a co-sputtering method. The structural and optical properties of the Gd-doped ZnO films were studied as a function of different Al doping concentrations. The X-ray diffraction profiles indicated that the films had a nanocrystalline structure of ZnO with a (0 0 2) preferential orientation. An increase in the Al doping concentration deteriorated the (0 0 2) diffraction peak intensity. The transmittance measurements in the UV–Vis wavelength range indicated that the film’s optical gap increased with increase in Al doping concentration. The heterojunction parameters were evaluated using the current–voltage (I-V) characterization carried out of the fabricated n-ZnO/p-Si heterostructure, in dark conditions at room temperature. From these measurements, the n-ZnO-based DMS/p-Si heterojunction diode with the use of (Gd, Al) co-doped ZnO film showed the lowest leakage current of 1.28 × 10−8 A and an ideality factor n of 1.11, close to the ideal diode behavior of η = 1, compared to the n-Gd-doped ZnO/p-Si and n-undoped ZnO/p-Si heterojunction diodes.

Effect of Co-Doping of Al3+, In3+, and Y3+ on the Electrical Properties of Zinc Oxide Varistors under Pre-Synthesizing BiSbO4

“…This can also be explained by the fact that at low doping concentrations, In 3+ is rapidly and mostly solidified into the ZnO lattice, but the solidification is limited by the fact that the ionic radius of In 3+ (ion radius of 8.0 × 10 −11 m) is larger than that of Zn 2+ (ion radius of 7.4 × 10 −11 m), and thus the diffraction angles of the three strongest peaks are almost the same at doping ratios of 0.6%, 0.8%, and 1.0%. At the same time, this also confirms the theory that "larger ion doping will move the XRD diffraction peaks to a lower diffraction angle, while smaller radius ion doping will move the corresponding diffraction peaks to a higher diffraction angle" [32,34]. This peak shift indirectly reflects the solid solution of In 3+ ions in ZnO grains.…”

“…This slight decrease in lattice parameter values. This is due to the presence of small stresses in the ZnO structure, which leads to the enlargement of the single cell of the ZnO lattice [ 32 ]. This can also be explained by the fact that at low doping concentrations [ 33 ], In 3+ is rapidly and mostly solidified into the ZnO lattice, but the solidification is limited by the fact that the ionic radius of In 3+ (ion radius of 8.0 × 10 −11 m) is larger than that of Zn 2+ (ion radius of 7.4 × 10 −11 m), and thus the diffraction angles of the three strongest peaks are almost the same at doping ratios of 0.6%, 0.8%, and 1.0%.…”

“…The radius of Al 3+ is smaller than that of Zn 2+ , and the absolute value of the difference between the two is larger, so Al 3+ is easy to solid-solve into ZnO grains, generating a large number of electronic charges, lowering the grain resistance, and keeping the residual pressure ratio low [ 32 , 36 , 39 ]. At the same time, Al 3+ doping induces a significant increase in the N d and a slight increase in the surface state density [ 21 ], which together lead to a decrease in .…”

Green Synthesis of Er-Doped ZnO Nanoparticles: An Investigation on the Methylene Blue, Eosin, and Ibuprofen Removal by Photodegradation

“…The photocatalytic efficiency of semiconductor materials depends on various factors such as particle size, morphology, surface area, crystalline structure, and the presence of defects [ 16 , 95 , 96 , 97 ]. Apart from these factors, the recombination rate of photogenerated charges can impact the photocatalytic process.…”

“…In addition, the results indicate that the Er-doped ZnO-based photocatalyst promotes charge separation, improving photocatalytic efficiency. The photocatalytic efficiency of semiconductor materials depends on various factors such as particle size, morphology, surface area, crystalline structure, and the presence of defects [16,[95][96][97]. Apart from these factors, the recombination rate of photogenerated charges can impact the photocatalytic process.…”