- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Estimation of the lateral dimensions of epitaxial submonolayer CdSe/ZnSe quantum dots
摘要： CdSe fractional monolayer quantum dots (FMQDs) embedded in a ZnSe matrix were produced by atomic layer epitaxy with a nominal coverage of 0.5 monolayer. They have a thickness of a/2, where a is the strained perpendicular lattice constant of cubic CdSe. Their photoluminescence spectra at low temperature exhibit narrow and intense excitonic emission around 2.759 eV. Based on the experimental excitonic emission energy and applying the factorized-envelope approximation, we have estimated that the lateral dimensions of these FMQDs are around 4 - 5 nm and their density is ~ 3 × 1012 cm-2.
关键词： quantum dots size,fractional monolayer quantum dots,epitaxial quantum dots,submonolayer quantum dots,ultra-thin quantum dots,CdSe quantum dots
更新于2025-09-23 15:21:01
-
IN SITU SECOND-HARMONIC GENERATION CIRCULAR DICHROISM WITH SUBMONOLAYER SENSITIVTIY
摘要： In this work, we present an experimental setup for the in situ and ex situ study of the optical activity of samples, which can be prepared under ultra-high vacuum (UHV) conditions by second-harmonic generation circular dichroism (SHG-CD) over a broad spectral range. The use of a racemic mixture as a qualified reference for the anisotropy factor is described and, as an example, the chiroptical properties of 1.5 μm thick (multilayers) as well as sub-monolayer thin films of the R- and S-enantiomer of 1,1'-Bi-2-naphthol (BINOL) evaporated onto BK7 substrates were investigated.
关键词： Submonolayer sensitivity,Second-harmonic generation circular dichroism,Circular-linear dichroism
更新于2025-09-23 15:21:01
-
Carrier transport and recombination dynamics of InAs/GaAs sub-monolayer quantum dot near infrared photodetector
摘要： Here, we present a relative study of tunnel-induced photocarrier escape processes in a laterally coupled InAs sub-monolayer quantum dot-based photodetector (SML QD-PD) as a function of fractional coverage from 0.4 ML to 0.8 ML. Both by simulation and experiment, we have quantitatively described the temperature dependent interband photoresponse spectrally tuned in the near infrared region (835 nm–890 nm) on the basis of mutual competition between the interband carrier recombination and interdot tunneling lifetime with varying SML coverage. The progressively increasing recombination lifetime and decreasing interdot tunneling lifetime with increasing SML coverage has attributed to a faster photoresponse and greater responsivity. At higher coverage fraction, tunnel induced fast speed photocarrier transit through lateral array of SML QDs has been found to be capable of offering a faster temporal response (100 μs) with faithful reproducibility up to higher frequencies (1.3 KHz). Here, we report a powerful strategy to simultaneously tune responsivity, speed of time response and detectivity by externally controlling the SML coverage. This time response is measured to be nine times faster than a conventional SK QD photodetector. With increased coverage, inhibition of dark current due to trapping of injected charge carriers up to higher temperatures have resulted in high sustainable photodetectivity of 8 × 1011 cm Hz1/2 w?1 at ~250 K that offers near room temperature photodetection.
关键词： photoconductive gain,quantum dot photodetector,inter-dot tunneling,submonolayer coverage,near-infrared photoresponse,recombination dynamics,temporal photoresponse
更新于2025-09-23 15:19:57
-
[IEEE 2019 34th Symposium on Microelectronics Technology and Devices (SBMicro) - Sao Paulo, Brazil (2019.8.26-2019.8.30)] 2019 34th Symposium on Microelectronics Technology and Devices (SBMicro) - Investigation of the quantum confinement anisotropy in a submonolayer quantum dot infrared photodetector
摘要： A submonolayer quantum dot infrared photodetector (SML-QDIP) was grown on a GaAs(001) substrate by molecular beam epitaxy and processed using conventional optical lithography, wet etching and electron-beam metallization. Additionally, a side of the device was polished at 45 degrees in order to allow optical measurements with s- and p- polarized light. The electro-optical properties of the device were investigated both in normal incidence and at 45 degrees in order to study the quantum confinement of the SML-QD along the lateral and vertical directions. The s-to-p photocurrent ratio was found to be between 0.10 and 0.43, showing that, in this new type of quantum dot, the lateral confinement is still weaker than along the vertical direction, but is better than the one of conventional QDs fabricated in the Stranski-Krastanov growth mode. The maximum specific detectivity in normal incidence was 1.3×1011 cm Hz1/2/W at 30 K and 0.9V.
关键词： quantum dot,GaAs,molecular beam epitaxy,infrared detector,photolithography,submonolayer
更新于2025-09-16 10:30:52
-
High-detectivity infrared photodetector based on InAs submonolayer quantum dots grown on GaAs(001) with a 2?×?4 surface reconstruction
摘要： The submonolayer quantum dots of an infrared photodetector were grown by molecular beam epitaxy in the presence of a very low As ?ux and a 2 × 4 surface reconstruction in order to e?ectively nucleate small two-dimensional InAs islands that are required to form such nano-structures. A speci?c detectivity of 9.2 × 1010 cm Hz1/2 W?1 was obtained at 10 K with a bias of 1.0 V.
关键词： InAs submonolayer quantum dots,2 × 4 surface reconstruction,molecular beam epitaxy,infrared photodetector,GaAs(001)
更新于2025-09-12 10:27:22