All-optical transistor using deep-level defects in nitride semiconductors for room temperature optical computing
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The essential device for optical computing is an all-optical transistor in which a weak “gate” light controls the strong “source” light. Particularly promising for application in logic operations are all-optical transistors using quasiparticles in a semiconductor because they can be easily integrated into circuits in a way similar to that of conventional electronic ones. However, the practical development of such devices has so far been limited due to extreme difficulties in achieving room temperature operation. In this work, we proposed and numerically verified a scheme of the high-temperature stable all-optical transistor, where light controls light by using deep-level defects in non-polar InGaN/GaN heterostructure and photo-exited holes as an intermediate medium. The developed optical switching concept fulfills all criteria for the useful all-optical transistor listed in Miller, Nat. Photonics 4, 3 (2010), in particular fan-out and cascadability, which are the most difficult to meet. For the design of our transistor, we applied an entirely new approach to III-nitride device physics: we turned usually undesirable deep-level defects into a key, active element of the transistor in which they realize on and off operations. Due to this, the developed device was able to obtain excellent operation stability in a wide temperature range up to 500 K as well as an extremely high on/off ratio (106) and gain (100). Finally, in order to show that the proposed transistor concept is feasible, we performed the gated-photoluminescence experiment for metal–oxide–semiconductor GaN structures.Based on first-principles calculations, the structure, electronic and optical properties of g-C3N4/HfSSe heterojunctions have been systematically explored. We prove the stability of two heterojunctions by comparing the binding energies from six different stacking heterojunctions, which name are g-C3N4/SHfSe heterojunction and g-C3N4/SeHfS heterojunction, respectively. It is shown that both heterojunctions behave direct band gaps with type II band alignment. The charge is rearranged at the interface after the heterojunctions are formed, which results in the formation of the built-in electric field. In the ultraviolet, visible and near-infrared regions, excellent light absorption is found in g-C3N4/HfSSe heterojunctions.
Ultraviolet
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In this paper, the novel type of transistor known as a hybrid transistor is proposed, in which all types of transistors can be formed by using a microring resonator called a PANDA microring resonator. In principle, such a transistor can be used to form for various transistor types by using the atom/molecule trapping tools, which is named by an optical tweezer, where in application all type of transistors, especially, molecule and photon transistors can be performed by using the trapping tools, which will be described in details.
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The bi-directional negative resistance transistor (BNRT) is an integrated device composed of two npn longitudinal bipolar transistors with common base and collector as well as an npn lateral bipolar transistor with the same base. We can get S type negative resistance characteristics between the two emitter terminals of both longitudinal transistors E/sub 1/ and E/sub 2/. By photosensitizing the BNRT, we have designed and fabricated a photo-bidirectional negative resistance transistor (PBNRT) for the first time. This new optical switching device has both photo-sensitive and negative resistance characteristics in a same device. In this paper, the relationship between light intensity and gate voltage affecting the I-V characteristics of the PBNRT have been measured and analyzed. The characteristic parameters dependence on light intensity and gate voltage have been simulated with the ATLAS device simulator. The simulation results are in agreement with the experimental data.
Heterostructure-emitter bipolar transistor
Static induction transistor
Negative resistance
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This chapter demonstrates an investigation into the electronic characteristics of CuPc/F16CuPc, BP2T/F16CuPc, ZnPc/C60, VOPc/Ph3, and SnCl2Pc/F16CuPc organic heterojunctions. Organic heterojunctions are categorized according to their interface electronic structure, including accumulation heterojunctions, depletion heterojunctions, and accumulation/depletion heterojunctions. The formation of an organic heterojunction is explained by the mechanism of thermal emission of electrons and an energy band model. A unique law covering organic heterojunctions and inorganic heterojunctions is revealed, which extends the theory of semiconductor heterojunctions.
Organic semiconductor
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Forming semiconductor heterojunctions is a promising strategy to boost the efficiency of solar-driven photoelectrochemical (PEC) water splitting by accelerating the separation and transport of photogenerated charge carriers via an interfacial electric field. However, there is limited research considering the influence of electrolytes on the band alignment of the heterojunction under PEC conditions. In this work, we use a single crystal NiCo2O4/SrTiO3 (NCO/STO) heterojunction with atomic-precision controlled thickness as a model photoelectrode to study the band structure modulations upon getting in contact with the electrolyte and the correlation with the PEC activity. It is found that the band alignment can be tuned by the control of p-n heterojunction film thickness and regulated by the water redox potential (Eredox). When the Fermi level (EF) of the heterojunction is higher/lower than the Eredox, the band bending at the NCO/STO-electrolyte interface will increase/decrease after contacting with the electrolyte. However, when the band bending width of the NCO layer is thinner than its thickness, the electrolyte will not influence the band alignment at the NCO/STO interface. In addition, PEC characterization results show that the 1 nm NCO/STO heterojunction photoanode exhibits superior water-splitting performance, owing to the optimum band structure of the p-n heterojunction and the shorter charge transfer distance.
Band bending
Depletion region
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Semiconductor heterojunctions offer unique electrical and optical properties not otherwise found in nature. Growth methods are now available to create new novel heterojunction structures with state-of-the-art physical properties for next generation electronics. This chapter covers the unique interface features of semiconductor heterojunctions in terms of their geometrical, chemical, and electronic structure. For a particular application, one chooses semiconductors or semiconductor alloys based on both their energy gaps and their good lattice match. The lattice mismatch between heterojunction constituents leads to strain and ultimately the formation of lattice dislocations. Semiconductor-semiconductor heterojunctions can exhibit a variety of chemical structures including interdiffusion, chemical reactions, and interlayer effects. The chapter reviews both experimental and theoretical work to understand the nature of heterojunction band offsets as well as atomic-scale methods to control them. One approach to describe band offsets involves the alignment of charge neutrality levels in the two semiconductors.
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Abstract : A technique based on the use of x-ray photoelectron spectroscopy was developed to measure heterojunction band discontinuities with an uncertainty of + or - 0.04 eV and changes in band discontinuities for a specific heterojunction interface with an uncertainty of + or - 0.01 eV. This technique was used to investigate Ge-GaAs, GaAs-A1As, ZnSe-GaAs, and ZnSe-Ge heterojunctions. It was discovered that microscopic dipoles present at abrupt heterojunction interfaces can substantially affect observed band discontinuities. Variations in heterojunction band discontinuities as functions of crystallographic orientation, growth sequence, and growth conditions were observed. It was established that heterojunction band discontinuities depend on microscopic properties of the interface and cannot be predicted from individual semiconductor properties alone. Based on electrostatic considerations, it was shown that polar heterojunction interfaces cannot be atomically abrupt but must require at least two interfacial transition planes to be consistent with experimental observations.
Classification of discontinuities
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Two-dimensional transition-metal dichalcogenides are not only promising optoelectronic materials but also can improve the optoelectronic performances of perovskites by forming heterostructures. Here, the structural, electronic, and optical properties of four kinds of CsPbI3/MS2 (M = Mo, W) heterostructures have been comprehensively investigated by density functional theory. No matter what the heterostructure structures, the electronic structure and excellent transport properties of both CsPbI3 surface and monolayer MS2 can be preserved in the CsPbI3/MS2 heterostructures. Moreover, CsPbI3/MS2 heterostructures show type-II band alignment with indirect band gaps and charge transfers, which separate electrons and holes spontaneously. The light absorptions of CsPbI3 surfaces in the infrared, visible, and ultraviolet regions are enhanced upon forming heterostructures. Note that the performances of heterostructures are strongly dependent on the heterostructure structure. Pb–I-terminated CsPbI3/MS2 heterostructures exhibit lower tunneling barriers and larger band offsets, which may lead to higher circuit voltages and lower dark currents, but they show lower stabilities compared with Cs–I-terminated CsPbI3/MS2 heterostructures. Moreover, CsPbI3/MoS2 heterostructures demonstrate higher electric and optical performances than those of CsPbI3/WS2 heterostructures. Our findings provide a deep understanding of CsPbI3/MS2 heterostructures and suggest an effective way to improve the performance of perovskite optoelectronic devices, such as radiation detection.
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The PCE of Cs 2 PbX 4 –WSe 2 heterostructures is larger than the PCE of Cs 2 PbX 4 –MoSe 2 heterostructures. Cs 2 PbI 4 –WSe 2 heterostructure has the largest PCE (18%) among Cs 2 PbX 4 –MSe 2 heterostructures and has great potential application in solar cells.
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A single-emitter multiple-input transistor laser has been realized and demonstrated in signal mixing, yielding in the stimulated-recombination region near laser threshold frequency conversion with simultaneously an electrical and optical output signal. In the unique nonlinear region of compression of the transistor I-V characteristics (β≡ΔIC∕ΔIB, βspon>βstim), input signals f1=2GHz and f2=2.1GHz are converted into mf1±nf2 ranging from 0.1to8.4GHz. Stimulated emission (enhanced recombination) changes the transistor into a special form of nonlinear element, a special form of electronic processor or “switch.”
SIGNAL (programming language)
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