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Piezoelectric Modulation of Broadband Photoresponse of Flexible Tellurium Nanomesh Photodetectors
摘要： Flexible photodetector shows great potential applications in intelligent wearable devices, health monitoring, and biological sensing. In this work, single crystal β-tellurium nanowires were grown on flexible muscovite by molecular beam epitaxy, constructing high-density ordered nanomesh structure. The prepared photodetectors based on tellurium nanomesh exhibit excellent mechanical flexibility, fast response in a broad range from ultraviolet to near-infrared, and good photosensitivity. We found that the flexible photodetectors with Shottky contact drastically suppressed dark current, while the response speed was lowered in comparison to the devices with ohmic contact, as holes would take long time to tunnel through the Shottky barrier between metal and p-type Te. Moreover, photoresponse of flexible Shottky photodetectors can be modulated by piezoelectricity of tellurium, and pronounced photocurrent increase after many times of bend. Under external stress, polarization charges could tune Shottky barrier height of the metal/tellurium, resulting in variation of photocurrent. The research not only explores the broadband photoresponse and piezoelectric effect of tellurium nanomesh, but also promotes the integration and development of broadband flexible optoelectronic devices.
关键词： tellurium nanomesh,piezoelectric effect,broadband photoresponse,molecular beam epitaxy,flexible photodetector
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE Photonics Conference (IPC) - San Antonio, TX, USA (2019.9.29-2019.10.3)] 2019 IEEE Photonics Conference (IPC) - O-Band Quantum Dot Semiconductor Optical Amplifier Directly Grown on CMOS Compatible Si Substrate
摘要： We report the first demonstration of the O-band quantum dot semiconductor optical amplifier (QD-SOA) that is directly grown on CMOS compatible on-axis silicon substrate. The QD-SOA has a length of 3600 ????, tapered from 4 ???? to 5.5 ????, which can offer 29 dB on-chip gain and 22.8 dBm saturation output power with a minimum 7 dB fiber to fiber noise figure.
关键词： semiconductor optical amplifiers,molecular beam epitaxy,direct growth on silicon,Quantum dot devices
更新于2025-09-11 14:15:04
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Phenomenological description of strain relief in step-graded metamorphic buffer layers based on In x Al1 ? x As ternary solutions
摘要： Spatial distributions of the residual elastic strains in layers of step-graded metamorphic buffers of two different designs, grown via molecular beam epitaxy on the basis of InxAl1 ? xAs ternary solutions, are obtained by means of reciprocal space mapping. It is shown that with allowance for work hardening, which affects strain relief in buffer layers and increases the strain in dislocation-free layers, the mechanism of strain relief in the final buffer steps, and the residual elastic strain in a buffer dislocation-free layer, are governed by the same phenomenological law as in a single-layer heterostructure.
关键词： InxAl1 ? xAs ternary solutions,step-graded metamorphic buffer layers,strain relief,reciprocal space mapping,molecular beam epitaxy
更新于2025-09-11 14:15:04
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Investigation on the effect of indium composition on ultrafast carrier dynamics in InGaN alloys
摘要： In this letter, we investigated the effect of indium composition on carrier relaxation mechanisms in InGaN alloys. Four high quality alloys with indium composition from 25% to 75% were fabricated using energetic neutral atomic-beam lithography/epitaxy molecular beam epitaxy. Using sub-picosecond resolved photoluminescence at high carrier density, it was found the effective carrier lifetime extends with increasing indium composition. Moreover, the calculated initial carrier temperature also rises with higher indium composition. These results are consistent with the theoretical prediction that a greater phonon bandgap could reduce the carrier cooling rate to a certain extent via hot carrier bottleneck effect.
关键词： InGaN alloys,indium composition,carrier dynamics,photoluminescence,molecular beam epitaxy
更新于2025-09-10 09:29:36
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Heterogeneous integration of InAs/GaSb tunnel diode structure on silicon using 200 nm GaAsSb dislocation filtering buffer
摘要： An InAs/GaSb tunnel diode structure was heterogeneously integrated on silicon by solid source molecular beam epitaxy using a 200 nm strained GaAs1-ySby dislocation filtering buffer. X-ray analysis demonstrated near complete strain relaxation of the metamorphic buffer and a quasi-lattice-matched InAs/GaSb heterostructure, while high-resolution transmission electron microscopy revealed sharp, atomically abrupt heterointerfaces between the GaSb and InAs epilayers. In-plane magnetotransport analysis revealed Shubnikov-de Haas oscillations, indicating the presence of a dominant high mobility carrier, thereby testifying to the quality of the heterostructure and interfaces. Temperature-dependent current-voltage characteristics of fabricated InAs/GaSb tunnel diodes demonstrated Shockley-Read-Hall generation-recombination at low bias and band-to-band tunneling transport at high bias. The extracted conductance slope from the fabricated tunnel diodes increased with increasing temperature due to thermal emission (Ea ～ 0.48 eV) and trap-assisted tunneling. Thus, this work illustrates the significance of defect control in the heterointegration of metamorphic InAs/GaSb tunnel diode heterostructures on silicon when using GaAs1-ySby dislocation filtering buffers.
关键词： dislocation filtering buffer,silicon,tunnel diode,InAs/GaSb,heterogeneous integration,molecular beam epitaxy
更新于2025-09-10 09:29:36
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Surfactant-induced chemical ordering of GaAsN:Bi
摘要： We have examined the in?uence of an incorporating surfactant on chemical ordering in GaAsN:Bi alloys. Epitaxy with a (2 (cid:2) 1) reconstruction leads to the formation of GaAsN alloys, while the introduction of a Bi ?ux induces long-range chemical ordering of the {111} planes of GaAsN:Bi. We propose a mechanism in which Bi enhances the alignment of dimer rows along the [110] direction, facilitating N incorporation beneath surface dimers and Bi incorporation between dimer rows to form alternating N-rich and Bi-rich {111} planes. These ?ndings suggest a route to tailoring the local atomic environment of N and Bi atoms in a wide range of emerging dilute nitride-bismide alloys.
关键词： surfactant,molecular-beam epitaxy,chemical ordering,dilute nitride-bismide alloys,GaAsN:Bi
更新于2025-09-10 09:29:36
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Field Effect in PbSnTe:In Films with Low Conductivity in the Mode of Injection from Contacts and Space-Charge Limitation of the Current
摘要： At T = 4.2 K, a strong change (up to 4 times) in the space-charge-limited current (SCLC) is observed for the first time at samples based on semi-insulating PbSnTe:In films grown by molecular-beam epitaxy on BaF2(111) substrates. The obtained results agree with experiments on the effect of treatment of the surface of PbSnTe:In films on the space-charge-limited current with a variation in the current to 103 times or more. At a qualitative level, the model is considered which assumes the substantial contribution of localized surface states to space charge formed in the mode of space-charge-limited current due to the injection of charge carriers from contacts.
关键词： field effect,surface states,molecular-beam epitaxy,space-charge-limited current,PbSnTe:In films
更新于2025-09-10 09:29:36
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Epitaxial processing optimization and photoluminescence spectra of CdTe thin films grown on highly dissimilar SrTiO3 (001) by molecular beam epitaxy
摘要： Single crystalline CdTe epitaxial layers (CTELs) are grown on a highly dissimilar (001) SrTiO3 (STO) by molecular beam epitaxy. The optimized growth temperature is determined to be in the range of 210 °C–270 °C. The crystalline structures of the CTELs are characterized by X-ray di?raction (XRD). The lattice parameters of the CTELs are revealed by the in-plane and out-of-plane reciprocal space mapping, electron microscopy and electron di?raction, and the epitaxial relationships between ?lm and substrate are further summarized as: (111)CdTe || (001)STO, [1?10]CdTe || [010]STO and [11?2]CdTe || [100]STO. The optimized full width at half maximum is yielded to be ~108 arcsec. The high crystalline quality and sharp interface are highlighted by the appearance of well-de?ned fringes of the XRD patterns, electron microscopy and photoluminescence spectra. Finally, the possible growth mechanisms are discussed and compliant epitaxial mechanism can well account for the epitaxial growth of the CdTe(111)/STO(001) epitaxial system. The achievement of the epitaxial growth of the CTELs on (001) STO with atomic ?atness and high-crystalline quality will avail to the potential application in photo-electric devices and the further epitaxy of the Hg1-xCdxTe-based infrared detector materials.
关键词： Photoluminescence,Cadmium telluride,Strontium titanate,Epitaxial layers,Molecular beam epitaxy,Perovskite substrate
更新于2025-09-10 09:29:36
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Temporal stability and absolute composition issues in molecular beam epitaxy of AlGaAs/GaAs THz QCL
摘要： The operation of the terahertz quantum cascade lasers (THz QCL) is strongly dependent on the repeatable fabrication of the well and barrier layers with the certain thicknesses throughout the whole active region stack epitaxial growth. This emphasizes the importance of the strict control of the growth rates and the stability of Si and group III effusion cell fluxes during growth [1]. It was reported [2] that two THz QCLs based on nominally identical multilayer heterostructures Al0.15Ga0.85As/GaAs emit at the different frequencies of 2.59 and 2.75 THz because of unintentional small deviations in the GaAs and AlAs growth rates (4 and 1.6 % respectively). Authors [3] determined the thickness tolerance for working lasing heterostructures to be minimally above 2% while the structures with thickness deviation 4.3 and 6.5 % are not lasing. In [4] the Ga cell temperature has to be increased to maintain a GaAs constant growth rate while the Al cell temperature remains nearly constant because variation in AlAs growth rate can be neglected. By using such growth rate compensation technique the two nominally identical structures approximately 10 mkm overall thick were found to show thickness difference of ~ 1 %. Thus calibration procedures and accurate analysis techniques become crucial to provide enhanced metrology possibilities.
关键词： molecular beam epitaxy,metrology,AlGaAs/GaAs,terahertz quantum cascade lasers,growth rates
更新于2025-09-10 09:29:36
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Effect of SrTiO <sub/>3</sub> oxygen vacancies on the conductivity of LaTiO <sub/>3</sub> /SrTiO <sub/>3</sub> heterostructures
摘要： In this work, we report the formation of a conductive layer through oxygen vacancies in an underlying SrTiO3 (STO) layer due to the growth of LaTiO3 (LTO) and the resulting LTO thickness-dependent conductivity of the LTO/STO system. Crystalline LTO films were grown by molecular beam epitaxy on TiO2-terminated STO(001) single-crystal substrates and 8-unit-cell (u.c.) STO template layers grown on Ge(001), under partial pressures of molecular oxygen ranging from 10?10 to 10?7 Torr. Film crystallinity was studied by in situ reflection high-energy electron diffraction, ex situ X-ray diffraction, and ex situ transmission electron microscopy. Film composition and the existence of oxygen vacancies were confirmed by in situ X-ray photoelectron spectroscopy. LTO films grown on STO substrates at oxygen partial pressures of 10?10 Torr were optimally oxidized (1:1:3 La:Ti:O). However, LTO films grown on 8-u.c. templates of STO on Ge with oxygen partial pressures less than 10?7 Torr showed extensive reduction of the Ti oxide and desorption of Sr/SrO in the STO layer. LTO films began to over-oxidize when grown on STO single-crystal substrates at oxygen partial pressures greater than 10?10 Torr but were nearly optimally oxidized when grown on STO templates on Ge at oxygen partial pressures of 10?7 Torr. Electrical characterization showed a dependence of conductivity on the thickness of the LTO films, with sheet carrier densities reaching ～5 × 1016 cm?2 for 20-u.c. (8-nm-thick) LTO/STO grown at 10?10 Torr of oxygen, suggesting that significant conduction occurred throughout the STO substrate due to the formation of oxygen vacancies.
关键词： oxygen vacancies,conductivity,SrTiO3,molecular beam epitaxy,LaTiO3/SrTiO3 heterostructures
更新于2025-09-10 09:29:36