P-doped Semiconductor Research Articles

Anion exchange strategies in radical doped hole transporting material for high-efficiency perovskite solar cells

Perovskite solar cells (PSCs) have received significant attention due to their superior photovoltaic conversion capability. To date, most efficient PSCs use p-doped organic semiconductors as hole-transporting layers (HTL). Many evidences show that the generally used p-doping system, i.e. lithium bis(trifluoromethane)sulfonimide and air exposure threaten the reproducibility and stability of PSCs. Recently, free radicals doped HTL have been used to fabricate efficient PSCs without using anying harmful dopants. Herein, we found that the low doping efficiency of radials is due to a weak Madelung potential. We developed a spontaneous anion exchange to stabilize the radical doped HTL via introducing an additional anion into the host-guest system. Conductivity and interfacial charge transfer are significantly enhanced by regulating the size of anions. We found that the conductivity and device performance is increased when the size of the anion increases. As a result, a champion efficiency of 20.7% under AM 1.5G 1-sun irradiation is achieved, which is comparable with the conventionally doped HTL. Moreover, the solar cells showed significantly enhanced stability against the humidity stress, which we attribute to the use of HTLs devoid of environmental sensitive additives.

Phosphorous-doped cadmium sulfide hollow octahedrons for enhanced visible-light photocatalytic H2 evolution

Currently, promoting solar absorption ability and photoexcited charge separation and transfer of semiconductors is of significance for enhancing their solar-to-hydrogen (STH) efficiency. Hollow-structured design and element doping strategy have proven to be effective in strengthening solar absorption and manipulating the charge dynamics. Herein, an ingenious design of doping phosphors (P) into hollow-structured CdS octahedrons is applied for achieving effective photocatalytic hydrogen production. The P-doped CdS semiconductor has a hollow interior for enhancing the photon absorbance and a narrow bandgap with upshift of valence band for facilitating photoinduced charge separation and transport, all of which contribute to their improved photocatalytic performance. Consequently, the synergistic effect in the designed archicture leads to an enhanced hydrogen production rate of up to 9.58 mmol·g−1 h−1, being about 11.7 fold higher than the reported CdS nanorods. Our work offers a new way for developing other types of sulfur-based semiconductors towards effective solar-to-hydrogen conversion.

Electronic properties of diamond semiconductor materials: based on response surface model

Abstract Diamond, a wide bandgap semiconductor material, has excellent physicochemical properties. It has great potential for application in high temperature, high frequency, high power electronic devices and other high technology fields. In order to study the electronic properties of diamond more precisely, an AM-response surface model is developed in this paper to investigate the electronic structures of diamond, P-doped diamond and N-doped diamond surfaces in depth. It is shown that there are three forms of charge states in the single vacancy on the diamond surface. When E=0 V, the negative charge energy level is -0.5 mV, the positive charge is 1 mV, and the zero level remains 0. And its energy level is unstable. In contrast, the double vacancy charge on the diamond surface varies depending on the valence band taken by E, and only one charge state exists. When E<0, the diamond surface vacant electron nature is negative charge state. When E>0, it is positive charge energy level. The electronic properties of the P-doped diamond semiconductor material are calculated to have a constant positive charge (1 mV). The electronic property of N-doped diamond semiconductor material is constant negative charge (-1mV).

Urbach Rule in the Red-Shifted Absorption Edge of PET Films Irradiated with Swift Heavy Ions.

This paper presents a new analysis of the experimental transmission spectra of polyethylene terephthalate (PET) films before and after irradiation with swift heavy ions (SHI) films, as reported previously by the authors. It is shown that the absorption edge red shift for irradiated films contains two regions of exponential form, one of which is located in the UV region and the other at lower energy, mainly in the visible part of the spectrum. The behaviour of the transmission curves under different irradiating fluences demonstrates that these two regions reflect respectively the electron-enriched core of the latent track and its electron-depleted peripheral halo. The focal point method yields a bandgap energy of 4.1 eV for the electron-enriched core of the latent track, which is similar to n-doped semiconductors, and a bandgap of about 1.3–1.5 eV for the electron-depleted halo, similar to p-doped semiconductors. The boundary between the latent track cores and halos corresponds to a conventional semiconductor p-n junction. The values of the characteristic Urbach energy determined from experimental data correspond to the nonradiative transition energy between the excited singlet and triplet levels of benzene-carboxyl complexes in repeat units of the PET chain molecule. A parallel is drawn between the SHI-induced redistribution of electrons held in structural traps in the PET film and chemical redox reactions, which involve the redistribution of electrons in chemical bonds. It is suggested that alkali etching triggers the release of excess electrons in the latent track cores, which act as a catalyst for the fragmentation of PET chain molecules along the latent tracks of the SHI irradiation.

Electric-Field-Effect Spin Switching with an Enhanced Number of Highly Polarized Electron and Photon Spins Using p-Doped Semiconductor Quantum Dots.

Electric-field-effect spin switching with an enhanced number of highly polarized electron and photon spins has been demonstrated using p-doped semiconductor quantum dots (QDs). Remote p-doping in InGaAs QDs tunnel-coupled with an InGaAs quantum well (QW) significantly increased the circularly polarized, thus electron-spin-polarized, photoluminescence intensity, depending on the electric-field-induced electron spin injection from the QW as a spin reservoir into the QDs. The spin polarity and polarization degree during this spin injection can be controlled by the direction and the strength of the electric field, where the spin direction can be reversed by excess electron spin injection into the QDs via spin scattering at the QD excited states. We found that the maximum degrees of both parallel and antiparallel spin polarization to the initial spin direction in the QW can be enhanced by p-doping. The doped holes without spin polarization can effectively contribute to this electric-field-effect spin switching after the initial electron spin injection selectively removes the parallel hole spins. The optimized p-doping induces fast spin reversals at the QD excited states with a moderate electric-field application, resulting in an efficient electric-field-driven antiparallel spin injection into the QD ground state. Further excess hole doping prevents this efficient spin reversal due to multiple electron–hole spin scattering, in addition to a spin-state filling effect at the QD excited states, during the spin injection from the QW into the QDs.

Passive mode-locking of p-doped quantum dot semiconductor lasers

Quantum dot based monolithic edge-emitting semiconductor lasers at 1.25 µm are ideal sources for the generation of broad optical frequency combs for optical communication applications. In this work, InAs/InGaAs quantum dot lasers with different total laser length to absorber length ratio and with different p-doping concentrations in the GaAs barrier sections are investigated experimentally in dependence on the gain injection current and absorber reverse bias voltage. A smaller mode-locking area is found for the p-doped device in dependence on the laser biasing conditions. For the undoped active region 1.3 ps short pulse widths at a pulse repetition rate of 20 GHz with a pulse-to-pulse timing jitter of 111 fs are reported for an absorber section length of 12% to the total cavity length. For an undoped and p-doped device short pulse emission between 2.5 ps and 5.5 ps is attained and a shorter absorber section length of 8% or 5%.

P-doped WO<sub>3</sub> semiconductor with enhanced conduction band on highly efficient photoelectrocatalytic reduction of CO<sub>2</sub>

Global warming is considered a serious climate problem caused by excessive emissions of carbon dioxide. Studies on catalytic conversion of CO2 are significant in terms of reducing CO2 concentration in the atmosphere, thus remain popular in the field. The photoelectrocatalytic (PEC) reduction of CO2 is an environment-friendly and efficient method to convert excessive CO2 into chemicals. With such conversion, the greenhouse effect can be alleviated through the storage and transformation of solar energy into chemical energy. WO3 is an n-type semiconductor with wide band gap and low conduction band position. Therefore, the use of WO3 is rare for photocatalytic water splitting and CO2 reduction. Although some techniques are used to improve the ability of WO3 in photocatalytic water splitting, the light quantum efficiency (AQE) is still less than TiO2. In current study, a facile method is explored to enhance the conduction band position of semiconductors, thereby improving the photoelectrocatalytic reduction of CO2. To the best of our knowledge, this is the first paper includes novel P-doped WO3 catalysts being designed, prepared, and used in the reduction of CO2 to carbon-based chemicals in water. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscope (TEM), and electron paramagnetic resonance (EPR) experiments were applied to confirm the formation of new catalysts. The photoelectric properties of new catalysts were characterized by UV-vis, linear sweep voltammetry (LSV), Mott-Schottky, and electrochemical impedance spectroscopy (EIS) experiments. We have developed a new type of hybrid semiconductor (P-doped WO3 vertical bar) as catalytic materials by introducing the vaporized phosphide (NaH2PO2) onto the surface of WO3 substrate under the flow of argon gas in a tube furnace. The PEC cell of P-doped WO3 vertical bar SCE vertical bar BiVO4 was equipped with a trielectrode system and powered by a chemical workstation, in which, p-doped WO3 vertical bar was used as photocathodes in photoelectrocatalytic reduction of CO2. The PEC cell was fulfilled with an electrolyte containing 1 mmol/L photosensitizer Eosin Y and 0.1 mol/L KHCO3, and bubbled with pure CO2 in 30 min to saturation, the experiment of CO2 reduction in water was carried out with a proper voltage under irradiation of simulated sun light (300W Xe lamp) to generate methanol, ethanol, acetone, etc. Our results indicates that the conduction band position of p-doped WO3 increases from -0.13 to -0.54 V along with the increase of P-doped quantity, augmenting its ability to reduce CO2. It can be seen that p-doped WO3 with oxygen vacancies has higher activity than pure WO3, in which, the highest activity is the catalyst 15-P, approaching to 0.4% AQE equal to natural plant, yielding methanol in a rate of 20.8 mu mol/(L h cm(2)) and acidic acid at a rate of 4.7 mu mol/(L h cm(2)). The influence of oxygen vacancies on the reaction is positive and verified by the quenching experiments of H2O2. The more oxidation time, the less oxygen vacancies. The EPR signal of 15-P catalyst treated by 2 h oxidation was reduced to 10%. The catalytic activity of CO2 reduction was decreased to 50%. In summary, we designed and prepared a new type of p-doped WO3 hybrid semiconductor material as efficient catalysts for photoelectrocatalytic reduction of CO2, resulting carbon-based chemicals. P-doped WO3 improves the conduction band position of the semiconductors, increases oxygen vacancies and defect sites. Therfore, the activity and efficiency of catalytic reduction of CO2 can be improved. The low voltage is favoured to ethanol production, and high voltage is favoured to acid production. The experimental results have guiding significance for the development of new hybrid semiconductor materials and their photoelectrocatalytic reduction of CO2.

Prediction of the structural and electronic properties of MoxTi1−xS2 monolayers via first principle simulations

Two-dimensional transition metal dichalcogenides have gained great attention because of their peculiar physical properties that make them interesting for a wide range of applications. Lately, alloying between different transition metal dichalcogenides has been proposed as an approach to control two-dimensional phase stability and to obtain compounds with tailored characteristics. In this theoretical study, we predict the phase diagram and the electronic properties of Mo xTi1− xS2 at varying stoichiometry and show how the material is metallic, when titanium is the predominant species, while it behaves as a p-doped semiconductor, when approaching pure MoS2 composition. Correspondingly, the thermodynamically most stable phase switches from the tetragonal to the hexagonal one. Further, we present an example which shows how the proposed alloys can be used to obtain new vertical two-dimensional heterostructures achieving effective electron/hole separation.

Thickness‐Dependent Electronic Transport in Ultrathin, Single Crystalline Silicon Nanomembranes

Adv. Electron. Mater., 2019, 5, 1900232 Some errors were present in the figure captions of this manuscript. The correction captions are reproduced below. Figure 1. Ultrathin Si-NM reduction process and corresponding characteristics. A) Schematic of our HF treatment process: thermal oxidation under 90% ozone atmosphere for 12 min at room temperature and stripping the oxide using 10% HF solution for 90 s. After 26 cycles, the thickness of Si-NM sample can be thinned from 50 to 10 nm. B) High-resolution TEM image of HF-thinned Si-NM. Inset is a corresponding diffraction spectroscopy image, indicating little surface reconstruction. C) High-resolution TEM of a 10 nm thick Si-NM. Figure 2. Basic electrical performance based on 10 nm thick Si-NM FETs. A) Schematic of the Si-NM FET structure. "Inset is a colorized optical microscope image of a Si-NM device (channel length L = 5 µm, width W = 10 µm) with the electrode area colored yellow. B) |IDS|–VDS curve at room temperature when VG is fixed at 1 V in a 10 nm thick Si-NM FET. Gate leakage current is plotted by black dots. C) Transfer characteristics of the Si-NM FET. Along the direction of the arrows, VDS changes by steps of 1 V. D) Band profiles of Si-NM FETs at various source-drain biases when VDS = 0, < 0, and > 0. Figure 3. The temperature-dependent property and analysis of Si-NM FETs with various thickness. A) Temperature-dependent IDS–VDS measurement of a 10 nm thick Si-NM FET when gate voltage VG is fixed at 0 V. B) Temperature-dependent conductivity of different thickness Si-NM. C) Re-plot of (B) using lnσ versus T−1/4 coordinates, where blue line shows acceptable linear fitting of 50 nm Si-NM data and others show obvious deviation from linear relationship. D) Re-plotted temperature-dependent conductivity of 10 nm thick Si-NM with lnσ versus lnT coordinate. Red and yellow dash line shows best linear fitting with T−η, η ≈ 0.5, and T3/2, respectively. The gray dash line shows an increasing tendency of conductivity for bulk p-doped semiconductor. E) Conductivity as a function of thickness at different temperatures (50 K, 100 K, 200 K and 300 K). The dots are experimental data and the solid line is a fitted curve. σ0 is the conductivity of 50-nm-thick Si-NM at each temperature.

Catastrophic Optical Damage in 950-nm Broad-Area Laser Diodes Due to Misaligned Optical Feedback and Injection

Improper back-coupling of optical feedback is a known cause for accelerated gradual degradation as well as catastrophic optical mirror damage of GaAs-based high-power semiconductor lasers. For those material systems emitting below the GaAs bandgap (870 nm at room temperature), such damage is induced by feedback-light absorption in the non-transparent cap layers and substrate, which intensifies the heating of the area close to the emission facet. For InGaAs/AlGaAs-based diode lasers in the spectral range from 880 to 1060 nm, however, all passive layers as well as the substrate are, with respect to interband absorption, transparent for the lasing wavelength so that, in this case, the degrading mechanism of misaligned optical feedback could not be explained entirely. By use of an experimental multi-device study of 950-nm broad-area lasers, we demonstrate that the threshold of catastrophic optical damage is decreased the most by positioning the feedback return spot such that it covers the p-side solder and the highly p-doped semiconductor layers. By means of thermoreflectance microscopy in conjunction with numerical simulations we find that such low damage thresholds are caused by a strong localization of the absorption of feedback light close to the laser front facet.

Band-to-Band Tunneling-Dominated Thermo-Enhanced Field Electron Emission from p-Si/ZnO Nanoemitters.

Thermo-enhancement is an effective way to achieve high performance field electron emitters, and enables the individually tuning on the emission current by temperature and the electron energy by voltage. The field emission current from metal or n-doped semiconductor emitter at a relatively lower temperature (i.e., < 1000 K) is less temperature sensitive due to the weak dependence of free electron density on temperature, while that from p-doped semiconductor emitter is restricted by its limited free electron density. Here, we developed full array of uniform individual p-Si/ZnO nanoemitters and demonstrated the strong thermo-enhanced field emission. The mechanism of forming uniform nanoemitters with well Si/ZnO mechanical joint in the nanotemplates was elucidated. No current saturation was observed in the thermo-enhanced field emission measurements. The emission current density showed about ten-time enhancement (from 1.31 to 12.11 mA/cm2 at 60.6 MV/m) by increasing the temperature from 323 to 623 K. The distinctive performance did not agree with the interband excitation mechanism but well-fit to the band-to-band tunneling model. The strong thermo-enhancement was proposed to be benefit from the increase of band-to-band tunneling probability at the surface portion of the p-Si/ZnO nanojunction. This work provides promising cathode for portable X-ray tubes/panel, ionization vacuum gauges and low energy electron beam lithography, in where electron-dose control at a fixed energy is needed.

Current-induced spin polarization in the isotropic k -cubed Rashba model: Theoretical study of p -doped semiconductor heterostructures and perovskite-oxide interfaces

Using the Matsubara Green's function formalism we calculate the temperature dependence of the nonequilibrium spin polarization induced by an external electric field in the presence of spin-orbit coupling. The model Hamiltonian includes an isotropic k-cubed form of the Rashba spin-orbit interaction. Such a Hamiltonian captures the electronic and spin properties of two-dimensional electron (hole) gas at the surfaces or interfaces of transition metal oxides or in p-doped semiconductor heterostructures. The induced spin polarization is calculated for the nonmagnetic as well as magnetic electron/hole gas. Relation of the spin polarization to the Berry curvature is also discussed.

Novel Strategies to Interface Molecules and 2D Materials

One of the most attractive areas of research in Nanoscience is the combination of 2D materials through van der Waals forces to form heterostructures (Novoselov, K. S.; Mishchenko, A.; Carvalho, A.; Castro Neto, A. H. Science 2016, 353, DOI: 10.1126/science.aac9439). Here, we present strategies beyond dispersion forces to interface 0D (molecules) and 2D materials. We will show examples of 0D-2D heterostructures connected through covalent and noncovalent chemistry. In the first example, we will show a method to functionalize graphene covalently with exquisite atomic selectivity and yield (NanoLett. 2016, Chem. Commun. 2017). In the second example, we will show that the photoresponse of MoS2 photodetectors can be enhanced by simple and reversible supramolecular functionalization with organic dyes (Chem. Commun. 2016). We will also show the example of a naturally occurring van der Waals heterostructure, franckeite, an air stable, p-doped semiconductor with photoresponse in the far IR (Nat. Comms. 2017). Finally, we will present strategies for the self assembly of liquid-phase exfoliated 2D materials from suspension into functioning electronic devices (Chem. Commun. 2017).

Heitler-London model for acceptor-acceptor interactions in doped semiconductors

The interactions between acceptors in semiconductors are often treated in qualitatively the same manner as those between donors. Acceptor wave functions are taken to be approximately hydrogenic and the standard hydrogen molecule Heitler-London model is used to describe acceptor-acceptor interactions. But due to valence band degeneracy and spin-orbit coupling, acceptor states can be far more complex than those of hydrogen atoms, which brings into question the validity of this approximation. To address this issue, we develop an acceptor-acceptor Heitler-London model using single-acceptor wave functions of the form proposed by Baldereschi and Lipari, which more accurately capture the physics of the acceptor states. We calculate the resulting acceptor-pair energy levels and find, in contrast to the two-level singlet-triplet splitting of the hydrogen molecule, a rich ten-level energy spectrum. Our results, computed as a function of inter-acceptor distance and spin-orbit coupling strength, suggest that acceptor-acceptor interactions can be qualitatively different from donor-donor interactions, and should therefore be relevant to the control of two-qubit interactions in acceptor-based qubit implementations, as well as the magnetic properties of a variety of p-doped semiconductor systems. Further insight is drawn by fitting numerical results to closed-form energy-level expressions obtained via an acceptor-acceptor Hubbard model.

Combined Electrochemical Impedance Spectroscopy, X-ray Photoelectron Spectroscopy, and Atomic Force Microscopy study of the distinct behavior of L-cysteine-thiolate formed at p- and n-GaAs(100) electrodes in Sodium Dodecyl Sulfate solution

Electrochemical impedance spectroscopy (EIS), X-ray spectroscopy (XPS), and atomic force microscopy (AFM) have been used to investigate the effects of the sodium dodecyl sulfate (SDS) interaction with the L-cysteine-thiolate covered p- and n-GaAs(100) electrodes in H2SO4 solution. The potential-induced reversible proton transfer found to occur within the L-cysteine-thiolate layer in the simple acid solution during the cathodic as well as the anodic potential scans at the p-doped semiconductor electrode and only in the anodic scan at the n-doped one is suppressed in both cases. XPS data revealed that the anionic surfactant has a complex interaction with the L-cysteine-thiolate covered GaAs(100) electrodes, which implicates both electrostatic and chemical forces. The SO42− head group interacts electrostatically with the NH3+ group of the cysteine-thiolate but it is also chemically involved in a chemisorption bond with the available Ga atoms. The amount of Ga-bound SDS species is much more pronounced at the L-cysteine-thiolate/p-GaAs(100) than at the L-cysteine thiolate/n-doped GaAs(100) electrodes meaning that cysteine-thiolate is mainly formed at As sites in the first case and at Ga sites in the latter one. This outcome strengthens the previous conclusions concerning the role of the dopant in determining the bonding way of the L-cysteine on GaAs(100) surfaces.

Polarization-entangled mid-infrared photon generation in p-doped semiconductor quantum wells

The optimal design of double quantum well structures for generation of polarization-entangled photons in the mid-infrared range, based on the valence intersubband transitions spontaneous parametric downconversion, is considered. The efficiency and frequency selectivity of the process are also estimated.

Electrical and optical conductivities of hole gas in p-doped bulk III–V semiconductors

We study electrical and optical conductivities of hole gas in p-doped bulk III-V semiconductors described by the Luttinger Hamiltonian. We provide exact analytical expressions of the Drude conductivity, inverse relaxation time for various impurity potentials, Drude weight, and optical conductivity in terms of the Luttinger parameters γ1 and γ2. The back scattering is completely suppressed as a result of the helicity conservation of the heavy and light hole states. The energy dependence of the relaxation time for the hole states is different from the Brooks-Herring formula for electron gas in n-doped semiconductors. We find that the inverse relaxation time of heavy holes is much less than that of the light holes for Coulomb-type and Gaussian-type impurity potentials and vice-versa for a short-range impurity potential. The Drude conductivity increases non-linearly with the increase in the hole density. The exponent of the density dependence of the conductivity is obtained in the Thomas-Fermi limit. The Drude weight varies linearly with the density even in the presence of the spin-orbit coupling. The finite-frequency optical conductivity goes as ω, and its amplitude strongly depends on the Luttinger parameters. The Luttinger parameters can be extracted from the optical conductivity measurement.

P-doped organic semiconductor: Potential replacement for PEDOT:PSS in organic photodetectors

In this work, we present an alternative to the use of PEDOT:PSS as hole transport and electron blocking layers in organic photodetectors processed by solution. As Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is known to be sensitive to humidity, oxygen, and UV, removing this layer is essential for lifetime improvements. As a first step to achieving this goal, we need to find an alternative layer that fulfills the same role in order to obtain a working diode with similar or better performance. As a replacement, a layer of poly[(4,8-bis-(2-ethylhexyloxy)-benzo(1,2-b:4,5-b′)dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiophene-)-2-6-diyl)] (PBDTTT-c) p-doped with the dopant tris-[1-(trifluoroethanoyl)-2-(trifluoromethyl)ethane-1,2-dithiolene] (Mo(tfd-COCF3)3) is used. This p-doped layer effectively lowers the hole injection barrier, and the low electron affinity of the polymer prevents the injection of electrons into the active layer. We show similar device performance under light and the improvements of detection performance with the doped layer in comparison with PEDOT:PSS, leading to a detectivity of 1.9 × 1013 cm (Hz)1/2 (W)−1, competitive with silicon diodes used in imaging applications. Moreover, contrary to PEDOT:PSS, no localization of the p-doped layer is needed, leading to a diode active area defined by the patterned electrodes.

Thermoelectric properties of homogeneously and non-homogeneously doped CdTe15/16M1/16 (M=N, P, As, Sb) and Cd15/16TeM1/16 (M=Na, K, Rb, Cs)

The electrical transport properties of p-doped semiconductors CdTe15/16M1/16 (M=N, P, As, Sb) and Cd15/16TeM1/16 (M=Na, K, Rb, Cs) with two configurations are investigated through first-principles calculations combined with Boltzmann transport theory under the relaxation time approximation. It is found that N and Cs atoms in the homogeneous structure induce much sharper electron densities of states (DOSs) and flatter energy bands at the valence band edges than the rest of doped elements, resulting in much larger Seebeck coefficients. The calculations reveal that most of the Seebeck coefficients and electrical conductivities are impacted unfavorably by the conglomeration of impurity atoms considered. Though the power factors for homogeneous doping of N and Cs are comparatively smaller, the electronic figures of merit are much larger at 800–1000K than the rest ones due to much smaller electronic thermal conductivities, therefore probably enhancing the thermoelectric figures of merit. The results show that doping the elements with electronegativities distinct from the host atoms can enhance the Seebeck coefficients and the thermoelectric performances of bulk semiconductors efficiently if the energy levels of doped atoms resonate with those of host atoms and the arrangement of doped atoms is modulated appropriately to avoid deteriorating the sharpness of the DOS (or transport distribution).

Spin initialization of a p-doped quantum dot coupled to a bowtie nanoantenna

The spin initialization of a hybrid system consisting of a p-doped semiconductor quantum dot coupled to a gold bowtie nanoantenna is analyzed. The quantum dot is described as a four-level atom-like system using the density matrix formalism. The two lower levels are Zeeman-split hole spin states and the two upper levels correspond to positively charged excitons with spin-up, spin-down hole pair and opposite spin electron. The gold bowtie nanoantenna is placed in close proximity to the quantum dot. A linearly polarized laser field drives two of the optical transitions of the quantum dot and produces localized surface charge oscillations in the nanoantenna which act back upon the quantum dot thus changing the effective field felt by it. The angular frequencies of those charge oscillations are very different along its two principal axes, resulting in an anisotropic modification of the spontaneous emission rates of the allowed optical transitions of the quantum dot. These changes are accounted for by using the Green tensor method, and result in a faster spin state initialization than that of the isolated quantum dot. We also show that the presence of the nanoantenna dramatically modifies the optical properties of the fluorescent photons, either in the spectral or in the time domain.