Mid-infrared photodetectors based on quaternary InAsSbP nanostructures

Quaternary InAsSbP quantum dots (QD) with the surface concentration of (3–5)×10⁹ cm⁻² have been grown on the InAs(100) substrate by the modified version of liquid-phase epitaxy. Morphology and distribution of densities of QDs were studied by means of atomic-force microscope. Diameter distribution of QDs was revealed to be Gaussian. The mean value of QD diameter is 23.1 nm with the variance of 6.9 nm. Two types of infrared photodetectors (IRPD) on the basis of InAs(100), with and without InAsSbP-QDs on the substrate surface, were fabricated and studied. Spectra of photoresponse of both types of IRPD at room temperature were measured and analyzed and a red shift was revealed for structures with QDs. Capacitance characteristics of IRPD and relative change in their surface resistance after irradiation with cw He-Ne laser have been studied.     

Intersubband transitions in quantum well mid-infrared photodetectors

A study of intersubband transitions in quantum well infrared detectors working at high temperatures has been reported. This study allows a greater tunability in the device designs, with the ability to control the peak wavelength, the absorption coefficient, the dark current, the quantum efficiency and the detectivity of the modeled structure operating around 3.3 μm wavelength. The detection energy and absorption coefficient dependences with an applied electric field are given. Then, the electro-optic performances of the modeled mid-infrared detector are estimated, the dark current dependence with the applied voltage and temperature as well as the quantum efficiency and the detectivity are investigated and discussed. High detectivities were found at high temperatures revealing the good performances of the designed photodetector, especially at 3.3 μm wavelength.     

Recent progress of infrared photodetectors based on lead chalcogenide colloidal quantum dots

Commercial photodetectors based on silicon are extensively applied in numerous fields. Except for their high performance, their maximum absorption wavelength is not over than 1100 nm and incident light with longer wavelengths cannot be detected; in addition, their cost is high and their manufacturing process is complex. Therefore, it is meaningful and significant to extend absorption wavelength, to decrease cost, and to simplify the manufacturing process while maintaining high performance for photodetectors. Due to the properties of size-dependent bandgap tunability, low cost, facile processing,and substrate compatibility, solution–processed colloidal quantum dots(CQDs) have recently gained significant attention and become one of the most competitive and promising candidates for optoelectronic devices. Among these CQDs, lead chalcogenide CQDs are getting very prominent and are widely investigated. In this paper, the recent progress of infrared(IR) photodetectors based on lead sulfide(PbS), lead selenide(PbSe), and ternary PbS_x Se_(1-x) CQDs, and their underlying concepts, breakthroughs, and remaining challenges are reviewed, thus providing guidance for designing high-performance quantum-dot IR photodetectors.     

Ultraviolet photodetectors based on wide bandgap oxide semiconductor films

Ultraviolet(UV) photodetectors have attracted more and more attention due to their great potential applications in missile tracking, flame detecting, pollution monitoring, ozone layer monitoring, and so on. Owing to the special characteristics of large bandgap, solution processable, low cost, environmentally friendly, etc., wide bandgap oxide semiconductor materials, such as ZnO, ZnMgO, Ga_2O_3, TiO_2, and Ni O, have gradually become a series of star materials in the field of semiconductor UV detection. In this paper, a review is presented on the development of UV photodetectors based on wide bandgap oxide semiconductor films.     

Photoluminescence kinetics of structures with InAs quantum dots for IR photodetectors

The experimental results of a photoluminescence kinetics study of InAs/GaAs structures with quantum dots grown by metal-organic vapor-phase epitaxy are shown. The measurements have revealed the fast capture of excited carriers from the GaAs barrier to quantum dots and slow interlevel relaxation inside the quantum dots.     

Quantum cryptography based on quantum dots

Network protocols are formulated for the phase-coding and correlated-photon-pairs quantum cryptosystems. These protocols are free of the restriction imposed on the distance between the two legitimate users by the transmission loss in the optical fiber. A single-photon source and a source of correlated photon pairs based on quantum dots are proposed. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 8, 646–651 (25 April 1996) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Qubits based on semiconductor quantum dots

Semiconductor quantum dots are promising hosts for qubits to build a quantum processor. In the last twenty years, intensive researches have been carried out and diverse kinds of qubits based on different types of semiconductor quantum dots were developed. Recent advances prove high fidelity single and two qubit gates, and even prototype quantum algorithms.These breakthroughs motivate further research on realizing a fault tolerant quantum computer. In this paper we review the main principles of various semiconductor quantum dot based qubits and the latest associated experimental results. Finally the future trends of those qubits will be discussed.     

Competing nucleation mechanisms and growth of InAsSbP quantum dots and nano-pits on the InAs(100) surface

InAsSbP quantum dots (QDs) and nano-pits (NPs) are grown on a InAs(100) surface by liquid phase epitaxy (LPE). Their morphology, dimensions and distribution density are investigated by high resolution scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction and total energy calculations. QDs average density ranges from 5 to 7 × 10⁹ cm^?2, with heights and widths having a Gaussian distribution with sizes from 5 nm to 15 nm and 10 nm to 40 nm respectively. The average pits density is (2–6) × 10¹⁰ cm^?2 with dimensions ranging from 5–30 nm in width and depth. We also find a shift in the absorption edge towards the longer wavelengths together with broadening towards shorter wavelengths indicating that these QDs and lateral overgrown nano-pits are grown at the n-InAs/p-InAsSbP heterojunction interface. Together with total energy calculations, the results indicate that lattice mismatch ratio plays a central role in the growth of these strain-induced nano-objects.     

Electro-optic switch based on near-field-coupled quantum dots

The propagation of exciton polaritons in near-field-coupled quantum-dot (QD) chains is modeled by a density-matrix formalism. It is shown that at least for low-temperature operation it is possible using electronically controlled switching by the quantum-confined Stark effect in such QD chains to rival and outperform room-temperature CMOS electronics in footprint and switch energy, though not in speed.     

Resonant-cavity-enhanced photodetectors and LEDs in the mid-infrared

In this paper we outline the use of resonant-cavity enhancement for increasing the exterior coupling efficiency of photodetectors and light-emitting diodes (LEDs) in the mid-infrared (MIR) spectral region. This method is potentially very important in the MIR because encapsulation is not presently feasible due to the lack of suitable materials. Among other potential applications, resonant-cavity-enhanced (RCE) photodetectors and LEDs could be particularly suitable for greenhouse gas detection because of their ‘pre-tunable’ spectrally narrowed resonantly enhanced peaks. We also present the optical characterization of an InAs RCE photodetector aimed at the detection of methane gas (λ≈3.3 μm), and an InAs/InAs_0.91Sb_0.09 resonant-cavity LED (RCLED) aimed at carbon dioxide gas (λ≈4.2 μm). The high peak responsivity of the RCE photodetector was 34.7 A/W at λ=3.14 μm, and the RCLED peaked at λ=3.96 μm. These are among the longest operating wavelengths for III–V RCE photodetectors and RCLEDs reported in the literature.     

The Ostwald ripening at nanoengineering of InAsSbP spherical and ellipsoidal quantum dots on InAs (100) surface

We present the results of growth of quasi-ternary InAsSbP spherical and ellipsoidal quantum dots (QDs) on InAs (100) surface by the method of liquid-phase epitaxy. Coarsening of QDs due to coalescence and Ostwald ripening was investigated by atomic-force and scanning electron microscopy. Ellipsoidal QDs prolated in [010] and oblated in [001] directions have been grown. Elongation ratios for the ellipsoidal QDs were measured in all three directions. It is shown that elongation of spherical QDs to ellipsoidal is started at QDs diameter of ～50 nm. Shape transformation of the QDs’ size distribution function from the Gram-Charlier-like to the Gaussian and then to the Lifshits-Slezov-like distribution was revealed at increasing the nucleation time.     

Theoretical study of quantum dots distribution function and the process of nucleation during Ostwald ripening in InAsSbP system

Experimental results on distribution of quantum dots versus sizes in InAsSbP system at different growth times are analyzed theoretically. It is shown that depending on growth time the process of nucleation and ripening of QDs is controlled either by transition kinetics in the grain-matrix boundary (Wagner distribution) or by the volume diffusion (Lifshitz-Slyozov distribution). Comparing theoretically calculated results with experimental data, numerical value of the reaction rate on the grain surface and the volume diffusion coefficient at nucleation temperature T = 550°C were estimated.     

Narrow spectral band monolithic lead-chalcogenide-on-Si mid-IR photodetectors

Narrow spectral band infrared detectors are required for multispectral infrared imaging. We review the first photovoltaic resonant cavity enhanced detectors (RCED) for the mid-IR range. The lead-chalcogenide (PbEuSe) photodetector is placed as a very thin layer inside an optical cavity. At least one side is terminated with an epitaxial Bragg mirror (consisting of quarter wavelength PbEuSe/BaF₂ pairs), while the second mirror may be a metal. Linewidths are as narrow as 37 nm at a peak wavelength of 4400 nm, and peak quantum efficiencies up to above 50% are obtained.     

Narrow spectral band monolithic lead-chalcogenide-on-Si mid-IR photodetectors

Narrow spectral band infrared detectors are required for multispectral infrared imaging. Wavelength selectivity can be obtained by placing passive line filters in front of the detectors, or, the preferred choice, by making the detectors themselves wavelength selective. We review the first photovoltaic resonant cavity enhanced detectors (RCED) for the mid-IR range. The lead-chalcogenide (PbEuSe) photodetector is placed as a very thin layer inside an optical cavity. At least one side is terminated with an epitaxial Brugg mirror (consisting of quarter wavelength PbEuSe/BaF₂ pairs), while the second mirror may be a metal. Linewidths are as narrow as 37 nm at a peak wavelength of 4400 nm, and peak quantum efficiencies up to above 50% are obtained. The paper presented there appears in Infrared Photoelectronics, edited by Antoni Rogalski, Eustace L. Dereniak, Fiodor F. Sizov, Proc. SPIE Vol. 5957, 59570B (2005).     

All-optical polarization switching based on Bragg-spaced quantum dots layers

One kind of Bragg-spaced all-optical switching has been proposed in this paper, and the quantum dots ensembles are used in it as active layers. By one-dimensional photonic crystal theory and transmission matrix method, we have studied the reflectivity stop band and switching effect based on the ac Stark effect. The reflectivity stop band of this switch can be suppressed or recovered, and the circular dichroism and birefringence are induced by a circle-polarized control light, which result in a significant polarization switching effect. This switching structure shows great advantages of lower requirement of pump light intensity, larger contrast ratio than that of Bragg-spaced quantum wells with the same period, especially this switching can be used at room temperature theoretically. So we predict that there are prodigious prospects for its using in high speed optical communications as all-optical switching.     

Hybrid structures based on quantum dots and graphene nanobelts

Optics and Spectroscopy - Luminescence and photoelectric properties of hybrid structures based on CdSe/ZnS quantum dots (QDs) and multilayer graphene have been investigated. A correlation between...     

光伏型太赫兹量子阱探测器研究进展

光伏型太赫兹量子阱探测器(PV-THzQWIP)是光伏型量子阱光电探测器(PV-QWIP)在THz波段的扩展,它具有功耗低、暗电流小、噪声水平低以及焦平面阵列(FPAs)热分辨率高等优点,是THz频段技术应用的重要器件之一.文章主要介绍了PV-THzQWIP的工作原理、特点、理论设计及其研究进展.     

光伏型太赫兹量子阱探测器研究进展

光伏型太赫兹量子阱探测器(PV-THzQWIP)是光伏型量子阱光电探测器(PV-QWIP)在THz波段的扩展,它具有功耗低、暗电流小、噪声水平低以及焦平面阵列(FPAs)热分辨率高等优点,是THz频段技术应用的重要器件之一.文章主要介绍了PV-THzQWIP的工作原理、特点、理论设计及其研究进展.     

基于量子点和MEH-PPV的白光发光二极管的研究

利用无机纳米材料与有机聚合物材料相结合的方法制备白光发光二极管器件, 研究了蓝光量子点QDs(B)掺杂聚[2-甲氧基-5-(2-乙基己氧基-1, 4-苯撑乙烯撑](MEH-PPV) 复合体系的发光特性及量子点QDs(B) 掺杂浓度(质量分数)不同对器件发光特性的影响. 制备了ITO/PEDOT:PSS/MEH-PPV:QDs(B)/LiF/Al 结构的电致发光器件, 测试了器件的电致发光光谱和电学、光学特性. 当QDs掺杂浓度为40%, 驱动电压为8 V时器件能得到较为理想的白光发射. 同时, 对比研究了非掺杂体系的发光特性, 制备了结构为ITO/PEDOT:PSS/MEH-PPV/QDs(B)/LiF/Al的器件, 掺杂体系相较于非掺杂体系, 器件的最大亮度增大, 启亮电压降低, 并分析了掺杂体系器件性能改善的原因.