Non-equilibrium Injection Research Articles

Thermalvoltaic Cell and toalleviate Climate Change with reversible Emission

Climate change, food scarce and energy crisis are some major problems we human are facing today, the development of the industry emitted excessive CO2 and it causes global warming effect since it is a gas with greenhouse effect. However, we need moderate CO2 emission to meet our demand to the energy for all individual and society activities that maintain our lives and realize our dreams. In fact, CO2 emission is reversible simply by afforesting and agricultural production, plant could just absorb CO2 and water as raw material for photosynthesis using sunlight as energy resource to produce carbohydrate which is the food for any creature on the earth. By accident, it was also found that heat could directly be converted into electricity by a thermal voltaic effect which just altered the non-equilibrium injection in a solar cell from photoemission into thermionic emission, or their combination, it could directly generate electromotive purely by absorbing heat from the environment with material that has thermionic emission under this temperature connected into the p-n junction of a photovoltaic cell, and graphene is promising since it may provide thermionic emission under room temperature more easily since it is a 2-dimensional semi-metal which has many novel properties such as massless electron and relativistic effect at low velocity and probably has no depletion effect with silicon. The CO2 emission could be reversed by more quality agricultural production and the excess heat in the environment could be directly absorbed to produce electricity by thermalvoltaic effect, in this way food scarce and energy crisis could resolve together with climate change, emission tax could be compensated by more production of vegetables and fruits or other vegetal growth.

Biasing topological charge injection in topological matter

We explore the interplay between topologies in the momentum and real spaces to formulate a thermodynamic description of nonequilibrium injection of topological charges under external bias. We show that the edge modes engendered by the momentum-space topology can play a functional role of connecting the external reservoirs to the bulk transport of topological charges in the real space. We illustrate our general results with two examples: the spin-torque injection of skyrmions in an electrically-biased integer quantum Hall system, and the vortex injection in a topological $p\,+\,i\,p$ superconductor coupled to heat reservoirs. Based on the universal fractional entropy of the Majorana zero modes bound to the vortices, their controllable injection proposed in this work could provide a route for creating and manipulating Majorana fermions.

Double Layer Structural Effects in Cyclic Voltammetry Curves Complicated with Non-Equilibrium Injection of Charge Carriers into Redox Polymer Films

An expressed asymmetry of cyclic voltammetry curves of electrodes modified with redox and conducting polymers is often considered as a consequence of slow injection of charge carriers into/out polymer films. The Butler-Volmer equation is usually applied to quantitative treatment of the rates of such injection processes. It is generally considered that the above equation does not take into account the influence of the double layer structure on the rates of electrode processes and, hence, one can assume that its use might lead only to a qualitative explanation of the observed asymmetry effect. Using different models of film double layers (at the film/electrode substrate and film/adjacent electrolyte interfaces) and the proper kinetic equations that include the so-called Frumkin correction, we have calculated the corresponding voltammetric curves in case of electrodes modified with redox polymer films. As expected, a good agreement between the data calculated and the results followed from the Butler-Volmer equation takes place only for the Helmholtz model of the both interfacial regions, while significant quantitative differences in such curves appear with using the Stern and Gouy models of film double layers.

Interband tunneling for hole injection in III-nitride ultraviolet emitters

Low p-type conductivity and high contact resistance remain a critical problem in wide band gap AlGaN-based ultraviolet light emitters due to the high acceptor ionization energy. In this work, interband tunneling is demonstrated for non-equilibrium injection of holes through the use of ultra-thin polarization-engineered layers that enhance tunneling probability by several orders of magnitude over a PN homojunction. Al0.3Ga0.7N interband tunnel junctions with a low resistance of 5.6 × 10−4 Ω cm2 were obtained and integrated on ultraviolet light emitting diodes. Tunnel injection of holes was used to realize GaN-free ultraviolet light emitters with bottom and top n-type Al0.3Ga0.7N contacts. At an emission wavelength of 327 nm, stable output power of 6 W/cm2 at a current density of 120 A/cm2 with a forward voltage of 5.9 V was achieved. This demonstration of efficient interband tunneling could enable device designs for higher efficiency ultraviolet emitters.

Magnetocurrent of ballistically injected electrons in insulating silicon

By using ballistic hot-electron injection to achieve lateral conduction through an otherwise fully insulating undoped silicon channel, we are able to study magnetic field suppression of charge transport in a regime normally excluded in Ohmic magnetoresistance measurements. Exceptionally large magnetocurrent changes of >16 000% at 45 K in magnetic fields of ≈2 T are observed, with differential reduction of over 6.2 T−1. Temperature-, electrostatic back-gate-, and magnetic field angle-dependence are presented. This phenomenon is attributed to strong space-charge effects in the dilute three-dimensional electron gas created by nonequilibrium injection.

Electrical Characterization of Impurity-Free Disordered p-Type GaAs

Impurity-free disordered p-GaAs epi layers by SiO 2 or native oxide capping are characterized using deep level transient spectroscopy (DLTS) and capacitance-voltage measurements. Samples, including an uncapped epi layer for reference, were annealed at 900°C for 30 s under Ar ambient. Disordering resulted in an increase in the free hole concentration with the effect being more pronounced for the SiO 2 capping layer. DLTS measurements revealed the corresponding increase in the concentrations of both the Cu and Zn-related deep levels in the disordered epi layers. We relate these changes in electrical properties to segregation effects resulting from the nonequilibrium injection of excess gallium vacancies in the disordered p-type epi layers. We discuss the relative merit of using either SiO 2 or native oxide layers for the integration of optoelectronic devices.

Experimental investigation of supercurrent enhancement in S–N–S junctions by non-equilibrium injection into supercurrent-carrying bound Andreev states

We report measurements on three-terminal superconductor–semiconductor–superconductor injection devices demonstrating enhancement of the supercurrent by injection from a superconducting injector electrode. Two other electrodes were used to form the detector junction. Applying a small voltage to the injector electrode reduced the maximum supercurrent (the critical current) between the detector electrodes. When the injector voltage was increased further (upto the gap voltage Δ/ e), the critical current between the detector electrodes increased and approached a new maximum. This is evidence of enhancement of the supercurrent by non-equilibrium injection into bound supercurrent-carrying Andreev states. The effect persists to temperatures where the equilibrium supercurrent has vanished.

Observation of Supercurrent Enhancement in SNS Junctions by Nonequilibrium Injection into Supercurrent Carrying Bound Andreev States

We report for the first time enhancement of the supercurrent by means of injection in a mesoscopic three terminal planar SN-SNS device made of Al on GaAs. When a current is injected from one of the superconducting Al electrodes at an injection bias $V\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{\Delta}(T)/e$, the dc Josephson current between the other two superconducting electrodes has a maximum, giving evidence for an enhancement due to a nonequilibrium injection into bound Andreev states of the underlying semiconductor. The effect persists to temperatures where the equilibrium supercurrent has vanished.

Dimension of inhomogeneous state in nonequilibrium superconductors

Spatially inhomogeneous order parameters are observed in super-conducting Pb-In films under large nonequilibrium injection of quasi-particles via tunneling. Critical sample dimension in which the inhomogeneous state appears is determined for the first time by means of a precise fabrication of tunnel injector and detector, and discussed in terms of several current models.

Observation of a New Superconducting State at High Quasiparticle Injection

The behavior of a superconducting A1 film under conditions of large nonequilibrium injection of quasiparticles is studied by means of a tunnel generator and detector. At a critical injection density, ${n}_{c}$, a second energy gap develops in the superconductor. The relevance to recent theories of nonequilibrium superconductivity is discussed.