P-type Conduction Properties Research Articles

Parameter modulation on p-type doping of AlGaN nanowires

The p-type doping process during the growth of AlGaN nanowires directly influences the optoelectronic properties of the related devices. However, research on the p-type ionization mechanism in AlxGa1-xN nanowires remains limited. In this work, we utilize first principles calculations to investigate p-type doping in AlxGa1-xN nanowires under different structural variables (Al component, doping element, doping site, and doping concentration). Our results demonstrate that p-type doping in AlxGa1-xN nanowires is an endothermic process, and increased dopant concentration leads to a decrease in system stability. Moreover, we found that dopant atoms are easier to substitute for Ga atoms than Al atoms. Among the three doping elements (Zn, Be and Mg), Zn exhibits the most challenging doping difficulty, while Be shows the easiest doping process, with Mg falling in between. Crystal Orbital Hamilton Population (COHP) and bond population calculations reveal the mechanism for the variation in doping structure stability. Doping induces a rearrangement of energy level orbitals, resulting in changes in the band gap. Specifically, the valence band exhibits an overall upward trend crossing the Fermi level, showing the p-type conductive properties. Notably, a significant decrease in electron density near Mg and Be leads to the formation of p-type conductive properties. The changes in hole density and effective mass further confirm the formation of p-type conductivity after doping. Additionally, structures with lower Al composition exhibit higher doping ionization degrees. This study is expected to provide a theoretical basis for the growth, preparation, and application of optoelectronic devices based on p-type AlGaN nanowires.

High-performance, low-power, and flexible ultraviolet photodetector based on crossed ZnO microwires p-n homojunction

Low-power, flexible, and integrated photodetectors have attracted increasing attention due to their potential applications of photosensing, astronomy, communications, wearable electronics, etc. Herein, the samples of ZnO microwires having p-type (Sb-doped ZnO, ZnO:Sb) and n-type (Ga-doped ZnO, ZnO:Ga) conduction properties were synthesized individually. Sequentially, a p-n homojunction vertical structure photodiode involving a single ZnO:Sb microwire crossed with a ZnO:Ga microwire, which can detect ultraviolet light signals, was constructed. When exposed under 360 nm light illumination at −0.1 V, the proposed photodiode reveals pronounced photodetection features, including a largest on/off ratio of 105, responsivity of 2.3 A/W, specific detectivity of ∼6.5×1013 Jones, noise equivalent power of 4.8×10−15 W Hz−1/2, and superior photoelectron conversion efficiency of ∼7.8%. The photodiode also exhibits a fast response/recovery time of 0.48 ms/9.41 ms. Further, we propose a facile and scalable construction scheme to integrate a p-ZnO:Sb⊗n-ZnO:Ga microwires homojunction component into a flexible, array-type detector, which manifests significant flexibility and electrical stability with insignificant degradation. Moreover, the as-constructed array unit can be integrated into a practical photoimaging system, which demonstrates remarkable high-resolution single-pixel imaging capability. The results represented in this work may supply a workable approach for developing low-dimensional ZnO-based homojunction optoelectronic devices with low-consumption, flexible, and integrated characteristics.

Thickness dependent studies on p-type K-doped ZnS nanostructured films grown via colloid-based solution route for ambipolar optoelectronic applications

Potassium-doped Zinc Sulphide (K:ZnS) nanostructured films were deposited on silica substrates using a colloid-based solution method, with varying thicknesses from 3 to 6 coats. The films exhibited p-type electrical conductivity and favorable optical properties for ambipolar and optoelectronic device fabrication. X-ray analysis confirmed a polycrystalline cubic phase in all the films, with crystallite sizes of 7–27 nm. Scanning electron micrographs revealed spherical globular grains of sizes 1.20–2.84 μm, leading to improved compactness with thicker films. UV/VIS analysis demonstrated a red-shifted band gap with increasing thickness. Photoluminescence under UV excitation revealed a peak at 477 nm attributed to K-induced trap levels. The electrical resistivity (1.34–6.00) × 102 Ω⋅cm, carrier concentration (4.63–13.33) × 1015 cm−3, and mobility (2.25–3.50) cm2/V·s varied with film thickness. The minimum resistivity of 1.34 × 102 (Ω⋅cm), maximum conductivity of 7.46 × 10−3 (Ω−1⋅cm−1), and highest mobility of 3.50 (cm2/V·s) were obtained for K:ZnS-6 film.

Effects of p-type conductive properties of triaxial strain-regulated ZnO (S, Se, Te) system

P-type ZnO materials are a difficult problem worldwide. The strain caused by doping, substrate and sample lattice constant mismatch, and thermal expansion coefficient mismatch is often ignored. First principle calculation is used to select the appropriate strain range and solve this problem. The effect equivalent to the actual strain is simulated to study the conductive properties and the mechanism of a doping system. Studies have shown that under unstrained conditions, the binding energies of undoped ZnO and all doped systems are negative, and the stability is relatively high. The formation energy of all doped systems increases, and their stability decreases with the increase in tensile strain or compressive strain. This study shows for the first time that when the compressive strain is −5%, the hole mobility of the same doping systems of Zn36SO35, Zn36SeO35, and Zn36TeO35 is relatively maximum. The difference between the hole concentration of the Zn36MO35 (M = S, Se, Te) systems is extremely small regardless of tensile strain or compressive strain. When the compressive strain is −5%, the hole conductivity of the Zn36SO35 system is the best. These findings can serve as guide in the experimental design and preparation of new p-type ZnO conductive functional materials.

Investigating N solubility in the host lattice of p-type Al- and N- co-doped SnO2 films with various N2 contents in sputtering gas

Abstract The Al3+–Sn4+ substitution into p-type Al- and N- co-doped SnO2 films enhances the N solubility in the SnO2 host lattice. The N solubility in the SnO2 host lattice increased with an increase in N2 content in the mixed sputtering gas, and the optimum N2 content was found to be 60 %, which corresponds to high film crystal quality and the lowest resistivity. The Al3+–Sn4+ and N3−–O2− substitution was verified using X-ray photoelectron spectroscopy (XPS), ultraviolet–visible spectroscopy, energy‐dispersive X‐ray (EDX), and X-ray diffraction (XRD) patterns. The SnO2 tetragonal rutile to cubic phase transformation indicated high N solubility in the SnO2 host lattice, while the Al3+–Sn4+ replacement was also verified by the crystal evolution of a (101) lattice reflection and the occurrence of the charge compensation effect. The best values achieved for resistivity, hole concentration, and hole mobility of the film were 6.4 × 10−3 Ω cm, 6.4 × 1019 cm−3, and 15.2 cm2 V−1 s−1, respectively. The current-voltage characteristics of films/n-Si heterojunctions under the illumination condition showed the p-type conductive properties of the films, and photocurrent response of the optimum film/n-Si heterojunction diode under the illumination condition of monochromatic wavelength light-emitting diodes (LEDs) exhibited a sufficient reproducible cycle and verified the N3−acceptor and VO donor levels in the bandgap.

Au nanoparticle modified single-crystalline p-type LaRhO3/SrTiO3 heterostructure for high performing VOCs sensor

Since the discovery of two-dimensional electron gas (2DEG) confined at perovskite LaAlO3/SrTiO3 (LAO/STO) interface, extensive efforts have been devoted to explore novel high-performance all oxide electronic devices, including gas sensors. Among perovskite oxides, LaRhO3 (LRO) possesses unique p-type conductivity and catalytic properties, which offer promising benefits for sensing volatile organic compounds (VOCs) molecules. In this work, single-crystalline p-type LRO thin film was epitaxially grown on STO (110) substrate as a high-quality sensing channel. Drastic improvement of sensing performance of LRO probed by 50 ppm ethanol was accomplished by appropriate Au decoration layer, e.g., an increased response (from 2.5 to 8.4), reduced optimal operation temperature (from 325 to 275 °C), decrease of response/recovery time (from 100/85 to 54/23 s) and improvement of detection limit (from 5000 to 250 ppb). X-ray photoelectron spectroscopy (XPS) indicates that Au nanoparticles facilitates the formation of reactive chemisorbed oxygen species, which substantially trigger the charge exchange occurring at ethanol/LRO interface. Our work highlights the importance of surface engineering toward high-performance perovskite based VOCs sensors.

Studying and fabricating optical, electrical, and structural properties of p-type Al- and N- co-doped SnO2 (ANTO) films and investigating the photo-electro effect of p-ANTO/n-Si heterojunctions

P-type SnO2 films co-doping Al and N increased the high solubility N in the SnO2 host lattice without degrading the crystal structure of the film. The solubility N in the SnO2 host lattice increased with the Al2O3 content in the ATO (Al2O3 doped SnO2) target, and the optimum Al2O3 content was found to be 6 %wt, which corresponds with the best film crystal quality. The optimum optical, electrical, and structural properties of films were achieved at a deposition temperature of 300 °C in a mixture of 50 % Ar and 50 % N2 gas from 6 %wt Al2O3-doped SnO2 target. The Al3+–Sn4+ and N3−–O2− substitution was verified using measurements, such as X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, and XRD patterns. Data regarding the tetragonal rutile to cubic phase transformation indicated the N3−–O2− substitution, while the Al3+–Sn4+ replacement was also verified by the appearance of an additional (101) lattice reflection. The resistivity, hole concentration, and hole mobility of the ANTO-6-50 film achieved the best values were 7.1 × 10−3 Ω cm, 6.24 × 1019 cm−3, and 14.1 cm2 V−1 s−1, respectively. The I–V characteristics of p-ANTO-x-50/n-Si heterojunctions under illumination showed p-type conductive properties of the ANTO-x-50 films and a good reproducible photocurrent response of the p-ANTO-x-50/n-Si heterojunction diodes.

Effect of Sn-substituted Ga and In dopant content on the structural, electrical, and optical properties of p-type X-doped SnO2 (X = Ga and In) films: Testing the photoelectronic effect of X-doped SnO2/n-Si junctions

To achieve the best p-type conductive properties of X-doped SnO2 (X = Ga, In) SnO2 film, a 9% wt X2O3 in SnO2 target is the best content for substitution at X sites in the SnO2 host lattice by X dopant where optimum In content replaces Sn, eliminating the lattice distortion in undoped SnO2 film. Optimum Ga content that replaces Sn enhances the lattice distortion but does not break the host lattice. The Ga3+–Sn2+ and In3+–Sn2+ substitution was verified using measurements such as X-ray photoelectron spectroscopy, photoluminescence, and ultraviolet-visible spectroscopy; the data for the (110) to (101) tetragonal rutile lattice plane changes indicated this replacement. The best p-type conductive properties achieved were 3.0 × 10−1 Ω cm, 6.20 × 1018 cm−3, and 3.01 cm2 V−1 s−1, respectively, for GTO. The respective values of the TIO films were 2.6 × 10−1 Ω cm, 1.24 × 1018 cm−3, and 19.35 cm2 V−1 s−1 for the resistivity, hole concentration, and hole mobility, respectively. The I–V characteristics of the In/p-GTO/n-Si/In and In/p-TIO/n-Si/In devices under illumination showed the p-type conductive properties of the GTO and TIO films.

Studying the influence of deposition temperature and nitrogen contents on the structural, optical, and electrical properties of N-doped SnO2 films prepared by direct current magnetron sputtering

This report focuses on studying and investigating in detail the structural, electrical, and optical properties of p-type N-doped SnO2 (NTO) versus the deposition temperature and nitrogen content. P-type transparent conductive NTO films were deposited on quartz glass substrates using a direct current (DC) magnetron sputtering method. The substitution of oxygen by nitrogen in the SnO2 host lattice was verified using measurements such as X-ray photoelectron spectroscopy. The position of the N3− defect state in the band gap was determined using photoluminescence and ultra-violet-visible spectroscopy measurements. The data for the (110) to (101) rutile lattice planes changed, and the rutile (plane (101)) to cubic (plane (111)) SnO2 phase transition indicated the substitution of oxygen by nitrogen in the SnO2 host lattice. The best p-type conductive properties achieved were 8 × 10−2 Ω cm, 1.36 × 1019 cm−3, and 6.75 cm2 V−1 s−1 for the resistivity, hole concentration, and hole mobility, respectively, for film deposited at the optimum substrate temperature of 300 °C in a gas mixture of Ar and 50% N2.

Investigation on the comparison of the structural, electrical and optical properties between ZCO:Na and ZCO:(Na, N) films synthesized by RF magnetron sputtering

Sodium doped ZnCdO (ZCO:Na) and sodium-nitrogen co-doped ZnCdO [ZCO:(Na, N)] films have been deposited on quartz substrates by radio frequency (RF) magnetron sputtering followed by a post-annealing treatment. The Hall-effect measurement results emphasized the importance of the dopant and annealing conditions in realizing p-type conversion. The ZCO:(Na, N) film annealed at 655°C for 30min (denoted sample F) showed optimal p-type conduction properties, which has the carrier concentration of 7.84 × 1018cm−3. Compared to the best p-type conduction of the ZCO:Na film (sample C), sample F reveals an increased carrier concentration (up from 1017 to 1018cm−3) owing to the formation of NaZn and No dual acceptors. Furthermore, the XPS results revealed that sample F has a higher NaZn acceptor content than sample C. The ZCO:(Na, N) films exhibited better crystal quality compared to the ZCO:Na films based on comparison of the values of full width at half maximum and intensity. It was found that the band gap (Eg) of all ZCO:Na and ZCO:(Na, N) films were smaller than that of pure ZnO due to Cd doping, and that the Eg increased with the increase of Tann, which is ascribed to the fact that more Cd atoms were evaporated from the films at higher Tann. In addition, the Eg of the ZCO:(Na, N) films (samples E-G) are generally larger than that of the ZCO:Na films (samples A-D). This is attributed to the incorporation of N in ZCO:(Na, N), as the No acceptor impedes the formation of Vo defects, resulting in a decrease in the formation of the CdZn-Vo complex, which in turn decreased the Cd concentration.

Investigation on Na-N dual acceptors doped p-type ZnCdO thin films synthesized by RF magnetron sputtering

Sodium and nitrogen dual acceptors doped ZnCdO [ZCO:(Na, N)] have been prepared by radio frequency (RF) reactive magnetron sputtering followed by rapid annealing treatment, and the influence of the ratio of argon to nitrogen gas flow (Ar:N2) on the electrical, structure and optical properties of ZCO:(Na, N) films were investigated in detail. Hall-effect measurement results reveal that Na–N dual acceptors doping method is an effective path to realize the p-type conversion of ZnCdO (ZCO). When the Ar:N2 was set to 1:2 (S3), ZCO:(Na, N) film possesses the optimal p-type conduction properties with carrier concentration of 7.84 × 1018cm−3 and the resistivity of 30.9Ωcm. It is demonstrated that the presence of NaZn and No acceptors are answerable for the p-type behavior in ZCO:(Na, N) film by the analysis of X-ray photoelectron spectroscopy (XPS) results. All the ZCO:(Na, N) films are of hexagonal wurtzite crystal structure with highly (002) preferential orientation. As Ar:N2 increases from 1:4 (S1) to 2:1 (S5), the absorption edge gradually shifted to longer wavelength side. The observed p-type ZCO:(Na, N) films will open the door for practical applications in various optoelectronic devices.

Exfoliation of natural van der Waals heterostructures to a single unit cell thickness.

Weak interlayer interactions in van der Waals crystals facilitate their mechanical exfoliation to monolayer and few-layer two-dimensional materials, which often exhibit striking physical phenomena absent in their bulk form. Here we utilize mechanical exfoliation to produce a two-dimensional form of a mineral franckeite and show that the phase segregation of chemical species into discrete layers at the sub-nanometre scale facilitates franckeite’s layered structure and basal cleavage down to a single unit cell thickness. This behaviour is likely to be common in a wider family of complex minerals and could be exploited for a single-step synthesis of van der Waals heterostructures, as an alternative to artificial stacking of individual two-dimensional crystals. We demonstrate p-type electrical conductivity and remarkable electrochemical properties of the exfoliated crystals, showing promise for a range of applications, and use the density functional theory calculations of franckeite’s electronic band structure to rationalize the experimental results.

Growth and characterization of large CeAlO3 perovskite crystals

This study is focused on obtaining large CeAlO3 single crystals. Using Czochralski and Edge-Defined Film Fed Growth techniques, crystals of length up to 130mm were obtained. The crystals belong to the tetragonal low temperature modification of CeAlO3, space group P4/mmm, a=3.7669Å, с=3.7967Å. Density and crystallographic parameters as well as some optical, luminescence and magnetic properties of CeAlO3 were studied. The crystals demonstrate rather bright luminescence under UV-excitation, while no luminescence has been registered under X-rays. Ceramic and single crystalline CeAlO3 samples demonstrate p-type conductivity and promising paramagnetic properties.

High-index Cu2O (113) film on faceted MgO (110) by molecular beam epitaxy

We report the growth of single-oriented Cu2O (113) film on faceted MgO (110) substrate by radio-frequency plasma assisted molecular beam epitaxy. A MgO {100} faceted homoepitaxial layer was introduced beforehand as a template for epitaxy of Cu2O film. The epitaxial relationship is determined to be Cu2O (113)//MgO (110) with a tilt angle of 4.76° and Cu2O [11¯0]//MgO [11¯0] by the combined study of in-situ reflection high-energy electron diffraction and ex-situ X-ray diffraction and transmission electron microscopy. The film demonstrates a good p-type conductivity and excellent optical properties, indicating that this unique approach is potentially applicable for high-index film preparation and device applications.

Fabrication and properties of Al–P codoped p-type zinc oxide films by RF magnetron sputtering

Al–P codoped ZnO (ZnO:(Al, P)) films were grown on quartz substrate by radio frequency magnetron sputtering using mixture of argon and oxygen as sputtering gas. Types of conduction and electrical properties in ZnO:(Al, P) films were found to be dependent on oxygen partial pressure ratios in the sputtering gas mixture. When oxygen partial pressure ratio is 70 %, the codoped ZnO film had the best p-type conduction properties. It has room-temperature resistivity of 1.4 × 10−1 Ω cm, Hall mobility of 13.5 cm2/Vs and carrier concentration of 3.7 × 1018 cm−3. The p-type conduction behavior of the ZnO:(Al, P) film was confirmed by the rectifying I–V characteristics of the p-ZnO:(P, N)/n-ZnO homojunction. The phosphorus-related acceptor energy level was estimated to be located 126 meV above the valence band. Mechanism of the p-type conductivity was discussed in the present work.

Physical properties of indium nitride, impurities, and defects

A review of the literature on the InN physical properties and state of impurities and defects in it based on the data published recently is presented. It is demonstrated that by the present time, significant progress has been made in synthesis of the material, study of its physical properties, and device making. It is established that InN has a band gap of 0.7 eV. Doping of InN with magnesium makes it possible to obtain layers with p-type conductivity and preset properties. The unique InN properties allow it to be considered as a promising material for a number of new devices.

Density of state effective mass and related charge transport properties in K-doped BiCuOSe

We report the enhanced p-type conduction properties in BiCuOSe by doping of monovalent ions (K+). As compared with undoped BiCuOSe, simultaneous increase in both the carrier concentration and the Hall mobility was achieved in the K-doped BiCuOSe. The origin of the enhancement was discussed in terms of the two-band structure in the valence band of the BiCuOSe, and the density of state effective masses of the heavy (∼1.1 me) and light hole (∼0.18 me) were estimated by using Pisarenko relation.

Fumarolic Activity, Acid-Sulfate Alteration, and High Sulfidation Epithermal Precious Metal Mineralization in the Crater of Kawah Ijen Volcano, Java, Indonesia

Abstract Opinion is divided over whether the fluid responsible for the formation of high sulfidation epithermal deposits is a vapor or a liquid, and whether it is entirely volcanic or of mixed volcanic-meteoric origin. Observations made at Kawah Ijen, an active stratovolcano (mainly andesitic in composition) located in the Ijen Caldera Complex in Java, Indonesia, are used to address these issues. The Kawah Ijen crater is approximately 1 km in diameter, and hosts one of the world’s largest hyperacidic lakes (pH ~0). On the lake edge is a small and actively degassing solfatara field, which is surrounded by a much larger area of acid-sulfate alteration. This area was exposed during a phreatomagmatic eruption in 1817, which excavated the crater to a depth of 250 m, and comprises zones of residual silica, alunite-pyrite, and dickite/kaolinite. Based on the fractionation of 34S and 32S between alunite and pyrite, the acid-sulfate alteration occurred at a temperature between 200° and 300°C. High sulfidation epithermal mineralization accompanied the alteration in the form of massive and vein-hosted pyrite that contains up to 192 ppb Au, 9.2 ppm Ag, 6,800 ppm Cu, and 3,430 ppm As; these elements are invisible at the highest resolution of scanning electron microscopy, and thus either occur in the form of nanoparticles or are in solid solution in the pyrite. Condensed fumarolic gases released from the solfatara field and sampled at temperatures between 330° and 495°C contain up to 3 ppm Cu and 3.8 ppm As; the concentrations of Au and Ag are below detection. The pH of the condensed gas (water vapor) is ~−0.5. The above observations support a model in which highly acidic gases condensed ~250 m beneath the floor of the crater. Depending on the fluid/rock ratio, the condensed liquids altered the andesitic host rocks by leaching them to leave behind a residue of “vuggy silica” (high fluid/rock ratio), by replacing the primary minerals with alunite and pyrite (intermediate fluid/rock ratio), or by converting them to dickite/kaolinite (lower fluid/rock ratio). Gold-, silver-, and copper-bearing phases were undersaturated in the condensed liquids. However, they were able to concentrate by adsorbing on the surfaces of the growing pyrite crystals, which developed p-type conductive properties as a result of the uptake of arsenic. The metals were incorporated in the pyrite either by their electrochemical reduction to form native metal nanoparticles or through coupled substitutions with arsenic for iron and sulfur. The results of this study provide compelling evidence that high sulfidation epithermal precious metal mineralization can form directly from condensed magmatic gases.

First principle study of the influence of vacancy defects on optical properties of GaN

We employ plane-wave with ultrasoft pseudopotential method to calculate and compare the total density of states and partial density of states of bulk-phase GaN, Ga0:9375N, and GaN0:9375 systems based on the first-principle density-functional theory (DFT). For Ga and N vacancies, the electronic structures of their neighbor and next-neighbor atoms change partially. The Ga0:9375N system has n-type semiconductor conductive properties, whereas the GaN0:9375 system has p-type semiconductor conductive properties. By studying the optical properties, the influence of Ga and N vacancy defects on the optical properties of GaN has been shown as mainly in the low-energy area and very weak in high-energy area. The dielectric peak influenced by vacancy defects expands to the visible light area, which greatly increases the electronic transition in visible light area.

Defect chemistry and proton-dopant association in BaZrO3 and BaPrO3

Defect reactions, water incorporation and proton-dopant association in the BaZrO3 and BaPrO3 perovskite materials are investigated using well-established atomistic simulation techniques. The interatomic potential models reproduce the experimental cubic BaZrO3 and orthorhombic BaPrO3 structures. The high defect energies suggest that significant intrinsic disorder (either Frenkel, Schottky or reduction) in BaZrO3 is unlikely, which is consistent with the relative chemical stability of this system. In contrast, favourable redox processes are found for intrinsic reduction of BaPrO3, and oxidation of acceptor-doped BaPrO3, the latter leading to p-type conduction properties as observed experimentally. Binding energies for dopant-OH pairs in BaZrO3 indicate the weakest association for Gd and Y dopants, and the strongest association for Sc. The high binding energies for all the dopant-OH pair clusters in BaPrO3 suggest strong proton trapping effects, which would be detrimental to proton conductivity. The water incorporation or hydration energy is found to be less exothermic for BaZrO3 than for BaPrO3, the higher exothermic value for the latter suggesting that water incorporation extends to higher temperatures in accord with the available thermodynamic data. The energies and pathways for oxide ion migration in both materials are also investigated.