Successful P-type Doping Research Articles

Ion implantation induced p-type conductivity in FeS2 thin film

In pursuing sustainable energy solutions, thin-film solar cells based on the Copper zinc tin sulfide (CZTS) absorber material have garnered significant attention due to their earth-abundant and non-toxic composition. However, the modest efficiency demonstrated by CZTS solar cells has prompted researchers to investigate novel approaches to improve their performance. An area of potential advancement entails the integration of appropriate hole transport layers (HTLs). In this simulation-based study, we focused on FeS2 as a highly promising candidate for use as an HTL in CZTS-based solar cells. FeS2, traditionally considered n-type, was tailored to achieve p-type conductivity through the negative ion implantation (O, P, and As) process. 40 keV ion beam was utilized, with three doses (105, 1010, 1015 cm−2) applied for each ion beam. We demonstrate successful p-type doping of FeS2 with a hole concentration of ∼1020 cm−3 in case of 1015 cm−2 dose, paving the way for its integration as an effective HTL within the CZTS solar cell structure.

Chemically doped-graphene FET photodetector enhancement via controlled carrier modulation with an iron(III)-chloride

Graphene is an excellent material among the family of 2D materials due to its electronic and optoelectronic properties. The intentional modification of its electronic structure via doping processes holds immense significance regarding tailoring its properties for specific applications. We comprehensively investigated p-type doping in few-layer graphene field-effect transistors (FETs) on SiO2/Si substrates by utilizing Iron(III)-chloride (FeCl3) dopant solutions with varying concentrations that range from 5 mM to 50 mM in this study. The successful doping was confirmed via a meticulous Raman spectroscopy analysis, which revealed notable shifts in the peak positions and peak broadening post-doping. Electrical measurements, which include transfer curves at a fixed biasing voltage, provided further confirmation, which demonstrates a distinctive shift in the Dirac point from −1 V to +25 V when the FeCl3 concentrations were changed from 5 mM to 50 mM. The impact of doping on the photoresponse of the graphene device was systematically explored. The device exhibited a significant increase in responsivity and external quantum efficiency following the p-type doping, which indicates an enhanced performance in photodetection. This research validates the successful p-type doping of graphene and underscores its implications regarding optimizing the electrical and optoelectronic properties of graphene-based devices, which confirms its potential for advanced applications for electronic and optoelectronic technologies.

Zn-Doped P-Type InAs Nanocrystal Quantum Dots.

Doped heavy metal-free III-V semiconductor nanocrystal quantum dots (QDs) are of great interest both from the fundamental aspects of doping in highly confined structures, and from the applicative side of utilizing such building blocks in the fabrication of p-n homojunction devices. InAs nanocrystals (NCs), that are of particular relevance for short-wave IR detection and emission applications, manifest heavy n-type character poising a challenge for their transition to p-type behavior. The p-type doping of InAs NCs is presented with Zn - enabling control over the charge carrier type in InAs QDs field effect transistors. The post-synthesis doping reaction mechanism is studied for Zn precursors with varying reactivity. Successful p-type doping is achieved by the more reactive precursor, diethylzinc. Substitutional doping by Zn2+ replacing In3+ is established by X-ray absorption spectroscopy analysis. Furthermore, enhanced near infraredphotoluminescence is observed due to surface passivation by Zn as indicated from elemental mapping utilizing high-resolution electron microscopy corroborated by X-ray photoelectron spectroscopy study. The demonstrated ability to control the carrier type, along with the improved emission characteristics, paves the way towards fabrication of optoelectronic devices active in the short-wave infrared region utilizing heavy-metal free nanocrystal building blocks.

Unidentified major p-type source in SnSe: Multivacancies

Tin selenide (SnSe) is considered a robust candidate for thermoelectric applications due to its very high thermoelectric figure of merit, ZT, with values of 2.6 in p-type and 2.8 in n-type single crystals. Sn has been replaced with various lower group dopants to achieve successful p-type doping in SnSe with high ZT values. A known, facile, and powerful alternative way to introduce a hole carrier is to use a natural single Sn vacancy, VSn. Through transport and scanning tunneling microscopy studies, we discovered that VSn are dominant in high-quality (slow cooling rate) SnSe single crystals, while multiple vacancies, Vmulti, are dominant in low-quality (high cooling rate) single crystals. Surprisingly, both VSn and Vmulti help to increase the power factors of SnSe, whereas samples with dominant VSn have superior thermoelectric properties in SnSe single crystals. Additionally, the observation that Vmulti are good p-type sources observed in relatively low-quality single crystals is useful in thermoelectric applications because polycrystalline SnSe can be used due to its mechanical strength; this substance is usually fabricated at very high cooling speeds.

Realization of p-type gallium nitride by magnesium ion implantation for vertical power devices

Implementing selective-area p-type doping through ion implantation is the most attractive choice for the fabrication of GaN-based bipolar power and related devices. However, the low activation efficiency of magnesium (Mg) ions and the inevitable surface decomposition during high-temperature activation annealing process still limit the use of this technology for GaN-based devices. In this work, we demonstrate successful p-type doping of GaN using protective coatings during a Mg ion implantation and thermal activation process. The p-type conduction of GaN is evidenced by the positive Seebeck coefficient obtained during thermopower characterization. On this basis, a GaN p-i-n diode is fabricated, exhibiting distinct rectifying characteristics with a turn-on voltage of 3 V with an acceptable reverse breakdown voltage of 300 V. Electron beam induced current (EBIC) and electroluminescent (EL) results further confirm the formation of p-type region due to Mg ion implantation and subsequent thermal activation. This repeatable and uniform manufacturing process can be implemented in mass production of GaN devices for versatile power and optoelectronic applications.

Accuracy and Transferability of Ab Initio Electronic Band Structure Calculations for Doped BiFeO3

BiFeO3 is a multiferroic material and, therefore, highly interesting with respect to future oxide electronics. In order to realize such devices, pn junctions need to be fabricated, which are currently impeded by the lack of successful p-type doping in this material. In order to guide the numerous research efforts in this field, we recently finished a comprehensive computational study, investigating the influence of many dopants onto the electronic structure of BiFeO3. In order to allow for this large scale ab initio study, the computational setup had to be accurate and efficient. Here we discuss the details of this assessment, showing that standard density-functional theory (DFT) yields good structural properties. The obtained electronic structure, however, suffers from well-known shortcomings. By comparing the conventional DFT results for alkali and alkaline-earth metal doping with more accurate hybrid-DFT calculations, we show that, in this case, the problems of standard DFT go beyond a simple systematic error. Conventional DFT shows bad transferability and the more reliable hybrid-DFT has to be chosen for a qualitatively correct prediction of doping induced changes in the electronic structure of BiFeO3.

In-rich InGaN thin films: Progress on growth, compositional uniformity, and doping for device applications

A number of In-rich InGaN films with In contents in the 20–40% range have been grown at moderately low temperatures on sapphire and silicon substrates at high growth rates using a versatile molecular beam epitaxy-type technology that utilizes an energetic beam of N atoms called energetic neutral atom beam lithography and epitaxy to overcome reaction barriers in the group III-nitride system. Extensive characterization results on the crystalline, optical, and electrical properties of the In-rich InGaN materials are reported. It was found that N-rich growth conditions are required to produce materials that have excellent crystallinity, uniform compositions, and bright band edge photoluminescence. For In-rich InGaN growth on sapphire, electrical transport measurements show reasonably low carrier concentrations and high mobilities. Successful p-type doping of In-rich InGaN with ∼20% and ∼40% In contents is demonstrated, and preliminary results on the formation of a p–n junction are reported. For In-rich InGaN growth on Si, the film structural properties are somewhat degraded and carrier concentrations are considerably higher.

Infrared to vacuum-ultraviolet ellipsometry and optical Hall-effect study of free-charge carrier parameters in Mg-doped InN

Infrared to vacuum-ultraviolet spectroscopic ellipsometry and far-infrared optical Hall-effect measurements are applied to conclude on successful p-type doping of InN films. A representative set of In-polar Mg-doped InN films with Mg concentrations ranging from 1.2×1016 cm−3 to 3.9×1021 cm−3 is investigated. The data are compared and discussed in dependence of the Mg concentration. Differences between n-type and p-type conducting samples are identified and explained. p-type conductivity in the Mg concentration range between 1.1×1018 cm−3 and 2.9×1019 cm−3 is indicated by the appearance of a dip structure in the infrared spectral region related to a loss in reflectivity of p-polarized light as a consequence of reduced LO phonon plasmon coupling, by vanishing free-charge carrier induced birefringence in the optical Hall-effect measurements, and by a sudden change in phonon-plasmon broadening behavior despite continuous change in the Mg concentration. By modeling the near-infrared-to-vacuum-ultraviolet ellipsometry data, information about layer thickness, electronic interband transitions, as well as surface roughness is extracted in dependence of the Mg concentration. A parameterized model that accounts for the phonon-plasmon coupling is applied for the infrared spectral range to determine the free-charge carrier concentration and mobility parameters in the doped bulk InN layer as well as the GaN template and undoped InN buffer layer. The optical Hall-effect best-match model parameters are consistent with those obtained from infrared ellipsometry analysis.

Aluminum doped silicon carbide thin films prepared by hot-wire CVD: Influence of the substrate temperature on material properties

Successful p-type doping of μc-SiC:H with Al introduced from trimethylaluminum has been already demonstrated. In this work we focus on the influence of substrate temperature ( T S = 300–390 °C) on the Al-doping. As T S is reduced from 390 °C to 300 °C, the crystallinity decreases from 75% to 55% and the dark conductivity σ D decreases first by about three orders of magnitude before increasing again at T S = 300 °C. Both microstructure, as determined from Raman spectroscopy, and optical absorption are little affected by the change in T S . Upon annealing at 450 °C in vacuum, σ D increases typically by two orders of magnitude up to 10 −4 S/cm, which is explained by dopant activation as a result of hydrogen desorption. It is concluded that a process temperature > 350 °C is needed to obtain effective Al-doping for p-type μc-SiC:H thin films.

Advances in InN epitaxy and its material control by MBE towards novel InN-based QWs

Initial stage of MBE-epitaxy processes of InN on c -plane GaN template and successful p-type doping were studied. It was found that InN epitaxy proceeds through SK-mode and 1-ML-thick InN can be coherently grown on GaN. Successful p-type doping of InN was achieved by Mg doping levels from 10 18 to about 3×10 19 cm −3 . Overdoped Mg's introduced new donors in InN resulting in n-type conduction. Novel structure InN-based QWs consisting of coherent 1-ML-thick InN wells embedded in GaN matrix were proposed and fabricated. It was confirmed that extremely fine structure InN QWs with quite sharp and flat hetero-interface were fabricated by self-limiting growth mode under In-polarity growth regime at remarkably higher growth temperatures up to 650 °C.

Evidence forp-Type Doping of InN

The first evidence of successful p-type doping of InN is presented. It is shown that InN:Mg films consist of a p-type bulk region with a thin n-type inversion layer at the surface that prevents electrical contact to the bulk. Capacitance-voltage measurements indicate a net concentration of ionized acceptors below the -type surface. Irradiation with 2 MeV He+ ions is used to convert the bulk of InN:Mg from p to n-type, at which point photoluminescence is recovered. The conversion is well explained by a model assuming two parallel conducting layers (the surface and the bulk) in the films.

Fabrication of p-type doped ZnO thin films using pulsed laser deposition

Two new methods were investigated for the fabrication of p-type doped ZnO thin films in a conventional pulsed laser deposition apparatus, but using only pure materials as targets. One of these is a sequential method and consists in firing alternatively the laser on a pure ZnO target and either a monocrystalline InP target (for phosphorus doping) or a Bi2O3 ceramic target (for bismuth doping). The other method consists in taking advantage of the lithium diffusion into a ZnO thin film while being deposited on a c-LiNbO3 substrate at high temperature. Some structural and electronic properties of the ZnO material obtained using these methods were measured using secondary ion mass spectrometry, X-ray diffraction, laser photoluminescence and Hall apparatus respectively and compared with those obtained for pure n-type thin films. The main results of this study are as follows. The sequential deposition method was successful in incorporating InP in ZnO films but led to inhomogeneous In and P spatial distributions, while segregation of Bi2O3 within the ZnO was evidenced by both the X-ray diffraction and photoluminescence results. Electrical measurements have revealed n-type conductivity for the ZnO/InP and the ZnO/c-LiNbO3 thin films and a peculiar behaviour for the ZnO/Bi2O3 samples which could point out to successful p-type doping for films containing smaller amounts of Bi2O3.

Growth of nitrogen-doped p-type ZnO films by spray pyrolysis and their electrical and optical properties

Nitrogen-doped ZnO films were deposited on silicon (1 0 0) substrate using zinc acetate and ammonium acetate aqueous solution as precursors by ultrasonic spray pyrolysis. Successful p-type doping can be realized at optimized substrate temperature. The p-type ZnO films show excellent electrical properties such as hole concentration of ∼10 18 cm −3, hole mobility of ∼10 2 cm 2 V −1 s −1 and resistivity of ∼10 −2 Ω cm. In the photoluminescence measurement, a strong near-band-edge emission was observed, while the deep-level emission was almost undetectable in both undoped and N-doped ZnO films. The growth and doping mechanism of N-doped ZnO films were discussed.

Carbon doping of cubic GaN under gallium‐rich growth conditions

Successful p-type doping of cubic GaN by carbon grown under Ga-rich conditions is reported with maximum hole concentration of 6 × 1018 cm−3 and hole mobility of 19 cm2/Vs at room temperature, re-spectively. Cubic GaN:C was grown by rf-plasma assisted molecular beam epitaxy (MBE) on a semiinsulating GaAs (001) substrate (3 inches wafer). C-doping of the c-GaN was achieved by e-beam evaporation of a graphite rode with an C-flux of 1 × 1012 cm−2 s−1. Optical microscopy, Hall-effect measurements and room temperature photoluminescence were used for the investigation of the morphological, electrical and optical properties of cubic GaN:C. Under Ga-rich growth conditions most part of the carbon atoms were incorporated substitutially on N-site giving p-type conductivity. Our results verify that effective p-type doping of c-GaN can be achieved under Ga-rich growth conditions.

P-Type Doping of Cubic GaN by Carbon

Successful p-type doping of cubic GaN epilayers by carbon using an e-beam evaporation source is reported. At room temperature Hall-effect measurements of the C-doped cubic GaN epilayer gave hole concentrations and hole mobilities as high as 6 x 10 17 cm -3 and 200 cm 2 /Vs, respectively. The thermal activation energy of the C-acceptor is (215 ± 10) meV. Low temperature photoluminescence spectra show a new line appearing at 3.08 eV. The emission energy increases with increasing e-beam evaporation power. This 3.08 eV line is attributed to a C related donor acceptor (D 0 A 0 ) transition.

P-Type Doping of Cubic GaN by Carbon

Successful p-type doping of cubic GaN epilayers by carbon using an e-beam evaporation source is reported. At room temperature Hall-effect measurements of the C-doped cubic GaN epilayer gave hole concentrations and hole mobilities as high as 6 x 10 17 cm -3 and 200 cm 2 /Vs, respectively. The thermal activation energy of the C-acceptor is (215 ± 10) meV. Low temperature photoluminescence spectra show a new line appearing at 3.08 eV. The emission energy increases with increasing e-beam evaporation power. This 3.08 eV line is attributed to a C related donor acceptor (D 0 A 0 ) transition.

Doping Studies of n-Type CsBi4Te6 Thermoelectric Materials

ABSTRACTWe have previously reported the successful p-type doping of CsBi4Te6 which had a high figure of merit at temperatures below 300 K. In this study, several dopants were explored to make n-type CsBi4Te6. A program of measurements was performed to identify the optimum doping concentration for several series of dopants. The highest power factors occurred around 125 K for the 0.5% Sn doped CsBi4Te6 sample which had a power factor of 21.9 μW/cm•K2 and 1.0% Te doped CsBi4Te6 which had a power factor of 21.7 μW/cm•K2.

Electrical and optical properties of boronated tetrahedrally bonded amorphous carbon (ta-C:B)

Tetrahedrally bonded amorphous carbon (ta-C) is a predominately sp3-bonded semiconductor with a band gap of order 2 eV. It can be doped n-type using nitrogen but no successful p-type doping has been reported until now. On the other hand, it has recently been shown that the incorporation of boron reduces the intrinsic compressive stress of ta-C, while still maintaining its high fraction of sp3 sites. This paper reports a detailed study of the electrical properties of boron-doped ta-C (ta-C:B). The ta-C:B films are deposited in a filtered cathodic vacuum arc system using a pressed cathode of graphite and boron powder. The composition and structure of the films are examined by electron energy loss spectroscopy. We find that the room temperature conductivity of the films increases by five orders of magnitude with a boron concentration from 0 to 8%. The conductivity activation energy decreases for the same boron concentration, while the E04 gap remains constant. N-type silicon/ta-C:B heterojunctions show a rectifying behaviour as a function of the boron concentration of the films. The films show photo-conductivity. The combined results indicate p-type doping of ta-C.

First-principles study of phosphorus and nitrogen impurities in ZnSe.

Phosphorus and nitrogen defects in ZnSe have been studied by pseudopotential total-energy calculations. Various charge states of the phosphorus and nitrogen impurities ocupying zinc sites (antisite defects) and interstitial sites (interstitial defects) were considered: their structural and electronic properties were investigated, and formation energies were calculated as a function of Se and electronic chemical potentials. The calculated electronic properties and formation energies were used in the investigation of the role of impurities in the p-type doping problem of ZnSe. Our study suggests that the difficulty with p-type doping of ZnSe by phosphorus results from the compensation of the shallow acceptors by the antisite defects ${\mathrm{P}}_{\mathrm{Zn}}$ which act as triple donors. In the case of nitrogen, the concentrations of the antisite and interstitial defects are too low to cause such compensation, which is consistent with the successful p-type doping of ZnSe with nitrogen.

Advances in the development of graded injector visible light emitters

Novel visible light emitters with low turn-on voltages and efficient room temperature operation have been demonstrated in the n-CdSe/p-ZnTe heterojunction separated by a graded Mg x Cd 1− x Se injecting region. The successful p-type doping of ZnTe up to 1 × 10 20 cm -3 using a nitrogen plasma source has allowed using higher quality GaSb substrates and growing of p-ZnTe epilayers. Diodes with ideality factors of 1.8 are realized with turn-on voltages near that of the bandgap of ZnTe. This deviation from an ideality of 1 may be due to using too small a peak Mg concentration in the Mg n Cd 1− x Se layer resulting in a barrier for electron injection and increasing recombination at the interface.