Enhanced P-type Conductivity Research Articles

Enhanced p-type conductivity of hexagonal boron nitride by an efficient two-step doping strategy

The present study proposes a two-step doping strategy for achieving efficient Mg doping of h-BN, involving an additional post-annealing treatment. This approach leads to ∼108-fold enhancement in conductivity of h-BN, compared with the as-doped h-BN grown by low-pressure chemical vapor deposition. The mechanism for large enhancement in h-BN doping efficiency after post-annealing was investigated, providing evidence that this treatment not only facilitates the nanoparticle decomposition and incorporation of Mg atoms into h-BN, but also restores its lattice defects. The efficient two-step doping strategy for p-type h-BN in this study enlightens its promising prospects for ultraviolet optoelectronic devices.

Hydrogen passivation of acceptor defects in delafossite CuMO2 (M = Al, Ga, In): Insights for enhanced p-type conductivity

Transparent conducting oxides with p-type conductivity hold immense potential for various electronic applications. The role of native point defects in delafossite CuMO2 (M = Al, Ga, In) as the source of p-type conductivity has been widely acknowledged. However, understanding the primary defects governing the electrical properties and devising strategies for improvement remains a critical challenge. In this study, we employ range-separated hybrid density functional calculations to elucidate the impact of acceptor defects and their interactions with hydrogen on electrical conductivity. Our findings demonstrate that hydrogen plays a pivotal role in controlling p-type conductivity in these oxides. Our investigation reveals that the interactions between hydrogen interstitial Hi and copper vacancy VCu lead to the formation of stable complexes that are electrically inactive. Considerable binding energies are observed for Hi–VCu complexes, indicating that they are highly bound complexes with low formation energy and, thus, high concentrations under both O-rich and O-poor conditions. A second hydrogen can be bound to VCu to form 2Hi–VCu complexes, which are thermodynamically stable and function as a single donor. Furthermore, hydrogen can bind with the antisite acceptor defects, CuM, forming Hi–CuM complexes. However, the lower binding energies associated with these complexes suggest likely dissociation into isolated Hi and CuM at relatively low temperatures. By shedding light on the strong influence of hydrogen passivation of acceptor defects, this study offers valuable insights into p-type conductivity in delafossite CuMO2.

Enhanced p-Type Conductivity of NiOx Films with Divalent Cd Ion Doping for Efficient Inverted Perovskite Solar Cells.

The effect of substitutional metal dopants in NiOx on the structural and electronic structures is of great interest, particularly for increasing the p-type conductivities as a hole transport layer (HTL) applied in perovskite solar cells (PSCs). In this paper, experimental fabrications and density functional theory calculations have been carried out on Cd-doped NiOx films to examine the effect of divalent doping on the electronic and geometric structures of NiOx. The results indicate that divalent Cd dopants reduced the formation energy of the Ni vacancy (VNi) and created more VNi in the films, which enhanced the p-type conductivity of the NiOx films. In addition, Cd doping also deepened the valence band edge, reduced the monomolecular Shockley-Read-Hall (SRH) recombination losses, and promoted hole extraction and transport. Hence, the PSCs with Cd:NiOx HTLs manifest a high efficiency of 20.47%, a high photocurrent density of 23.00 mA cm-2, and a high fill factor of 79.62%, as well as negligible hysteresis and excellent stability. This work illustrates that divalent elements such as Cd, Zn, Co, etc. may be potential dopants to improve the p-type conductivity of the NiOx films for applications in highly efficient and stabilized PSCs.

Prospects for hole doping in dilute-anion III-nitrides

Efficient p-type doping of III-nitride materials is notoriously difficult due to their large bandgaps, intrinsic n-type doping, and the large ionization energy of acceptors. Specifically, aluminum-containing nitrides such as AlN and AlGaN have demonstrated low p-type conductivity, which increases device resistances and reduces carrier injection in optoelectronic applications. Dilute-anion III-nitride materials are a promising solution for addressing this issue and increasing the activation efficiency of p-type dopants. The upward movement of the valence bands in these materials reduces the ionization energy of the dopants, allowing for enhanced p-type conductivity in comparison to the conventional nitrides. Incorporation of a dilute-arsenic impurity into AlN is hypothesized to significantly reduce the ionization energy of Mg-acceptors from 500 meV to 286 meV, allowing for a two-order magnitude increase in activation efficiency in 6.25%-As AlNAs over that of AlN.

Effects of electrochemical potentiostatic activation on carrier transport in AlGaN-based deep-ultraviolet light-emitting diodes

Electrochemical potentiostatic activation (EPA) is applied to AlGaN-based deep-ultraviolet (DUV) light-emitting diodes (LEDs). The effects of EPA on DUV LEDs are disclosed by analyzing the temperature-dependent current-voltage characteristics. EPA-treated DUV LEDs show improved electrical optical properties with suppressed forward leakage currents, reduced operation voltages, smaller ideality factors, and enhanced light emission compared to the reference device. EPA treatment yields distinct differences in carrier conduction across the p-AlGaN layer. The limited conductivity of the p-AlGaN layer in a DUV LED causes space-charge-limited (SCL)-like conduction behavior in the voltage regime far exceeding the turn-on voltage. EPA treatment alleviates the SCL-like conduction, which infers the improved conductivity of the p-AlGaN layer. In the same vein, the occurrence of high-level injection is retarded in the EPA-treated device, which is also consistent with enhanced conductivity of the p-AlGaN layer that mitigates asymmetry between n- and p-type conductivities of a DUV LED. Thus, the improved performance of AlGaN-based DUV LED is attributed to the promoted charge transport, which is enabled by the EPA-induced enhanced p-type conductivity.

P-type semi-transparent conductive NiO films with high deposition rate produced by superimposed high power impulse magnetron sputtering

High power impulse magnetron sputtering (HiPIMS) technology with extremely high target ionization rate is employed to deposit Ni3+-rich NiO films with enhanced p-type conductivity. However, the HiPIMS technique possesses a significant disadvantage; that is, its low deposition rate. In order to overcome this drawback, superimposed HiPIMS ( HiPIMS+MF) power supply was employed in this work. The influence of the MF pulse duration on the films’ composition, morphology, chemical status, structure and optoelectronic properties is investigated here. The results show that compared with pure HiPIMS deposition, the deposition rate of superimposed HiPIMS technology is significantly improved. Meanwhile, the advantages of HiPIMS with high ionization rates are retained. Ni3+-rich NiO films are produced using superimposed HiPIMS deposition. Especially in HiPIMS+MF 3X deposition mode, a relatively low resistivity of 3.41 Ω cm with high deposition rate (2.32 Å/s) is realized.

Hillock assisted p-type enhancement in N-polar GaN:Mg films grown by MOCVD

We report on the enhanced incorporation efficiency of magnesium dopants into facets of hexagonal hillock structures in N-polar GaN, studied by comparative analysis of GaN:Mg films grown by MOCVD on high and low hillock density GaN template layers. Total magnesium concentration in planar regions surrounding a hillock structure is comparable to that within hillock sidewall facets measured at 1.3 × 1019 cm−3 by atom probe tomography, and clustering of Mg atoms is seen in all regions of the film. Within individual hillock structures a decreased Mg cluster density is observed within hillock structures as opposed to the planar regions surrounding a hillock. Additionally, the Mg cluster radius is decreased within the hillock sidewall. The favorable incorporation of Mg is attributed to Mg dopants incorporating substitutionally for Ga during growth of semi-polar facets of the hillock structures. Enhanced p-type conductivity of GaN:Mg films grown on high hillock density template layers is verified by optical and electrical measurement.

Solution Combustion Synthesis: Low-Temperature Processing for p-Type Cu:NiO Thin Films for Transparent Electronics.

Low-temperature solution processing opens a new window for the fabrication of oxide semiconductors due to its simple, low cost, and large-area uniformity. Herein, by using solution combustion synthesis (SCS), p-type Cu-doped NiO (Cu:NiO) thin films are fabricated at a temperature lower than 150 °C. The light doping of Cu substitutes the Ni site and disperses the valence band of the NiO matrix, leading to an enhanced p-type conductivity. Their integration into thin-film transistors (TFTs) demonstrates typical p-type semiconducting behavior. The optimized Cu5% NiO TFT exhibits outstanding electrical performance with a hole mobility of 1.5 cm2 V-1 s-1 , a large on/off current ratio of ≈104 , and clear switching characteristics under dynamic measurements. The employment of a high-k ZrO2 gate dielectric enables a low operating voltage (≤2 V) of the TFTs, which is critical for portable and battery-driven devices. The construction of a light-emitting-diode driving circuit demonstrates the high current control capability of the resultant TFTs. The achievement of the low-temperature-processed Cu:NiO thin films via SCS not only provides a feasible approach for low-cost flexible p-type oxide electronics but also represents a significant step toward the development of complementary metal-oxide semiconductor circuits.

Mg Incorporation Efficiency in Pulsed MOCVD of N-Polar GaN:Mg

We report on the effect of growth polarity and pulsed or $$\delta $$ -doped growth mode on impurity incorporation in metalorganic chemical vapor deposition-grown GaN. In Ga-polar orientation, up to 12× enhancement in Mg concentration for given Mg flow rate is observed, resulting in enhanced p-type conductivity for these samples. In contrast, this enhancement effect is greatly diminished for N-polar samples, falling off with increasing Mg flow and showing maximum enhancement of 2.7× at 30 nmol/min Mg flow. At higher Mg flow rates, Mg incorporation at normal levels did not correspond to p-type conductivity, which may be due to Mg incorporation at nonacceptor sites. Concentrations of C, O, and Si were also investigated, revealing dependence on Mg flow in N-polar pulsed samples. Carbon incorporation was found to decrease with increasing Mg flow, and oxygen incorporation was found to remain high across varied Mg flow. These effects combine to result in N-polar samples that are not p-type when using the pulsed growth mode.

Na‐Diffusion Enhanced p‐type Conductivity in Cu(In,Ga)Se2: A New Mechanism for Efficient Doping in Semiconductors

Na‐Diffusion Enhanced p‐type Conductivity in Cu(In,Ga)Se₂: A New Mechanism for Efficient Doping in Semiconductors

Electronic and magnetic properties of second main-group and second sub-group metals substitution for Al in delafossite CuAlO2

A systematic theoretical investigation has been carried out for the structural, electronic and magnetic properties of second main-group and second sub-group metals substitution for Al in delafossite CuAlO2 in the framework of density functional theory. The structural parameters and formation energies were calculated and discussed. The appearance of enhanced p-type conductivity after doping has been analyzed. Moreover, it is shown that all dopants have relatively large magnetic moments, but their ferromagnetic states are unstable, showing that their potential application in dilute magnetic semiconductors is not applicable.

Device structure-dependent field-effect and photoresponse performances of p-type ZnTe:Sb nanoribbons

Sb-doped ZnTe nanoribbons (NRs) with enhanced p-type conductivity were successfully synthesized by a simple thermal co-evaporation method. Nanodevices, including nano-field-effect transistors (FETs) and nano-photodetectors (nanoPDs), were constructed based on the ZnTe:Sb NRs and their structure dependent device performances were systemically investigated. It is found that the transport properties of the ZnTe nanostructures as well as the device structures play a critical role in determining the device performances. In contrast to the nano-metal-oxide-semiconductor FETs (nanoMOSFETs) with back-gate structure, the top-gate nano-metal-insulator-semiconductor FETs (nanoMISFETs) show much enhanced performances in all aspects. On the other hand, owing to the appropriate p-type doping, nano-photodetectors (nanoPDs) based on the ZnTe:Sb NRs exhibit excellent device performances, such as high responsivity and photoconductive gain, fast response speed, large detectivity and so on. Moreover, the response time could be effectively shortened by using nano-heterojunction photodetectors (nanoHPDs). It is expected that knowledge gained from this work could be readily extended to nanodevices based on other nanostructures.

Oxygen rich p-type ZnO thin films using wet chemical route with enhanced carrier concentration by temperature-dependent tuning of acceptor defects

This paper reports the temperature-dependent tailoring of acceptor defects in oxygen rich ZnO thin films, for enhanced p-type conductivity. The oxygen rich p-type ZnO thin films were successfully grown by pulsed laser deposition on silicon substrate at different postdeposition annealing temperatures (500–800 °C). The oxygen rich ZnO powder was synthesized by wet chemical method using zinc acetate dihydrate [Zn(CH3COO)2·2H2O] and potassium hydroxide (KOH) as precursors. The powder was then compressed and sintered to make pellets for pulsed laser deposition system. The x-ray diffraction analysis exhibits an improved crystallinity in thin films annealed at elevated temperatures with a temperature-dependent variation in lattice constants. An analysis of Auger Zn L3M4,5M4,5 peak reveals a consistent decrease in interstitial zinc (Zni) exhibiting its temperature-dependent reversion to zinc lattice sites. Room temperature photoluminescence of the p-type ZnO shows a dominant deep level emission peak at ∼3.12 eV related to oxygen interstitials (acceptors). The relative concentration of oxygen interstitials (Oi) increases with increase in annealing temperature, resulting in enhanced hole carrier concentration. The maximum hole carrier concentration of 6.8 × 1014 cm−3 (indicating p-type conductivity) was estimated using Hall probe measurements for the thin film sample annealed at 700 °C.

Enhanced p-type conductivity of nitrogen doped ZnO by nano/micro structured rods and Zn-rich Co-doping process

We report the formation of p-type nitrogen doped ZnO (ZnO:N) grown by thermal-evaporation deposition. We found that the ZnO nano/micro structured rods can improve nitrogen doping. In addition, co-doping with metal (excess Zn in this study) can enhance nitrogen doping through a Zn-rich process. The effects of nitrogen precursors on the electrical and optical properties of ZnO:N were investigated. This study shows that growth process plays a critical role in the electrical properties of ZnO:N.

Annealing effects on the p-type ZnO films fabricated on GaAs substrate by atmospheric pressure metal organic chemical vapor deposition

The effects of post-annealing conducted at 500–650 °C on structural, electrical and optical properties of ZnO film fabricated on GaAs (1 0 0) substrate by atmospheric pressure metal-organic chemical vapor deposition are investigated. X-ray diffraction analyses show that the Zn 3As 2 and ZnGa 2O 4 phases are produced for the specimens post-annealed at 500 °C and above. Hall measurements indicate that stable p-type ZnO films with hole concentration ranging from 4.7 × 10 18 to 8.7 × 10 19 cm −3 can be obtained by modulating the annealing temperature from 500 to 600 °C. In particular, room-temperature photoluminescence (PL) measurements indicate that the superior-quality p-type film could be achieved by a post-annealing treatment at 600 °C. Moreover, low temperature PL spectra at 10 K are dominated by the acceptor-related luminescence mechanisms for the films post-annealed at 550 °C and above. The ionization energy of acceptor was calculated to be 133–146 meV, which is in good agreement with that theoretically predicted for the As Zn–2V Zn complex in ZnO. The interdiffused arsenic atoms in the film post-annealed at 600 °C are suggested to form the As Zn–2V Zn complex quite effectively, resulting in the most enhanced p-type conductivity and improved material quality.

Enhanced p-Type Conductivity of ZnTe Nanoribbons by Nitrogen Doping

Single-crystalline intrinsic and N-doped p-type ZnTe nanoribbons (NRs) were synthesized via the thermal evaporation method in argon-mixed hydrogen and nitrogen-mixed ammonia, respectively. Both intrinsic and doped ZnTe nanoribbons had zinc blende structure and uniform geometry. X-ray diffraction peaks of N-doped ZnTe nanoribbons had an obvious shift toward higher angle direction as compared with intrinsic ZnTe. X-ray photoelectron spectroscopy detection confirmed that the dopant content of nitrogen in ZnTe nanoribbons was close to 1%. Field-effect transistors based on both intrinsic and N-doped ZnTe nanoribbons were constructed. Electrical measurements demonstrated that N-doping led to a substantial enhancement in p-type conductivity of ZnTe nanoribbons with a high hole mobility of 1.2 cm−2 V−1 S−1 and a low resistivity of 0.14 Ω cm in contrast to the 6.2 × 10−3 cm−2 V−1 S−1 and 45.1 Ω cm for intrinsic nanoribbons. Moreover, the defect reaction mechanism was proposed to explain the p-type behaviors of bot...

Tuning chemistry of CuSCN to enhance the performance of TiO2/N719/CuSCN all-solid-state dye-sensitized solar cell

CuSCN with enhanced p-type conductivity was prepared by replacing some of the cuprous sites by triethylamine coordinated Cu(I) with concomitant (SCN)(2) doping to introduce more holes. A compound Cu(5)[(C(2)H(5))(3)N](3)(SCN)(11) was isolated and well characterized. A 41% enhancement of energy conversion efficiency of the TiO(2)/N719/modified CuSCN cell from the best reported value and more than a factor of ten from bare CuSCN was achieved.

Enhanced p-type conductivity and band gap narrowing in heavily Al doped NiO thin filmsdeposited by RF magnetron sputtering

Stoichiometric NiO, a Mott–Hubbard insulator at room temperature,shows p-type electrical conduction due to the introduction ofNi2+ vacancies(VNi′′) andself-doping of Ni3+ ions in the presence of excess oxygen. The electrical conductivity of this important materialis low and not sufficient for active device fabrication. Al doped NiO thin films were synthesizedby radio frequency (RF) magnetron sputtering on glass substrates at a substrate temperature of250 °C in anoxygen + argon atmosphere in order to enhance the p-type electrical conductivity. X-ray diffractionstudies confirmed the correct phase formation and also oriented growth of NiO thin films.Al doping was confirmed by x-ray photoelectron spectroscopic studies. The structural,electrical and optical properties of the films were investigated as a function of Al doping(0–4 wt%) in the target. The room temperature electrical conductivity increased from0.01–0.32 S cm −1 for 0–4% Al doping. With increasing Al doping, above the Mott critical carrier density,energy band gap shrinkage was observed. This was explained by the shift of the band edgesdue to the existence of exchange and correlation energies amongst the electron–electron andhole–hole systems and also by the interaction between the impurity quasi-particle system.

Synergism in binary nanocrystal superlattices leads to enhanced p-type conductivity in self-assembled PbTe/Ag2Te thin films

The ordered cocrystallization of nanoparticles into binary superlattices enables close contact of nanocrystals with distinct physical properties, providing a route to 'metamaterials' design. Here we present the first electronic measurements of multicomponent nanocrystal solids composed of PbTe and Ag(2)Te, demonstrating synergistic effects leading to enhanced p-type conductivity. First, syntheses of size-tuneable PbTe and Ag(2)Te nanocrystals are presented, along with deposition as thin-film nanocrystal solids, whose electronic transport properties are characterized. Next, assembly of PbTe and Ag(2)Te nanocrystals into AB binary nanocrystal superlattices is demonstrated. Furthermore, binary composites of varying PbTe-Ag(2)Te stoichiometry (1:1 and 5:1) are prepared and electronically characterized. These composites show strongly enhanced (conductance approximately 100-fold increased in 1:1 composites over the sum of individual conductances of single-component PbTe and Ag(2)Te films) p-type electronic conductivity. This observation, consistent with the role of Ag(2)Te as a p-type dopant in bulk PbTe, demonstrates that nanocrystals can behave as dopants in nanostructured assemblies.

Defect Structure，Electrical Property and Oxygen Permeation of Ba0.5Sr0.5Co0.8Fe0.2O3-δ

A study of oxygen permeation material Ba0.5Sr0.5Co0.8Fe0.2O3-δ（BSCF）is presented. The O2 -TPD，nonstoichiometry（δ），electrical conductivity（σ）and oxygen permeation were investigated. In the experiment of O2 -TPD，three oxygen-releasing peaks are observed：one peak at low temperature is attributed to the absorbed oxygen at the position of V··O，the other two peaks are related with the release of oxygen ions at two different positions in the BSCF crystal lattice. At 470℃，δ reaches minimum and σ achieves maximum：with increasing temperature，absorbed oxygen at the position of V··O is released，resulting in the first peak of O2 -TPD；the rest of absorbed oxygen entered BSCF lattice，causing the decrease of δ；the temperature dependence of the conductivity demonstrates increasing conductivity with temperatures up to a maximum at about 470℃，indicating thermally activated p-type semiconductivity，which changed to metallic conduction behavior above 470℃. Furthermore，the experiment shows that the σ maximum at the heating step is higher than that obtained at cooling step，which can be explained：when heating，some absorbed oxygen at the position of V··O enters the lattice，δ decreases and concentration of Co4+&Fe4+ increases，leading to an enhanced p-type conductivity of BSCF；on the other hand，when cooling from high temperature，absorbed oxygen at the position of V··O does not exist. In the experiment of oxygen permeation，BSCF proves to be a suitable material for oxygen-separating at above 850℃，its oxygen permeability JO2 is higher than 1 μmol/cm2 s with air as feed gas and He as sweep gas，the activation energy Ea is 63. 1 kJ/mol.