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Much attention has been paid to the photoresponse of vanaduim oxide (VOx) and amorphous silicon based microbolometer for long-wavelength infrared detection under un-cooled operation condition in recent decades. However, the outstanding physical and chemical properties of graphene and reduced graphene oxide (rGO) stimulate their potential for use in light-sensitive applications. Much less attention has been paid to investigate the performance on long-wavelength infrared detection of microbolometer using reduced graphene oxide/SiNx/vanadium oxide composite films deposited on under room temperature operation. In the research, we have proposed the novel microbolometer based on VOx/SiNx/rGO composite films replace the as-deposited VOx based microbolometer. It is noted that such extraordinary properties (high responsivity: 18,130 V/W and low NETD: 43.32 mK) of the VOx/SiNx/rGO composite presented here encourage us to contemplate on this protocol for next generation optoelectronic device engineering for infrared detection.

Various tantalum (Ta)-doped vanadium oxide (VOx:Ta) films with various Ta doping contents were deposited on the Si substrates as the sensitive layer of the floating-type microbolometers using a magnetron radio frequency (RF) co-sputtering system. The vanadium (V) target and the tantalum pentoxide (Ta2O5) target were used to deposit the VOx:Ta films. To improve the microbolometer responsivity by effectively reducing the thermal loss from the Si substrates, the floating-type microbolometers were fabricated using bulk micromachining technique. From the X-ray photoelectron spectroscopy (XPS) spectra, except the V2O5 and V6O13, the lower oxygen state of VOx films, such as VO2 and V2O3, were also obtained by doping Ta into the VOx films. Consequently, compared with the VO2 microbolometers, the VOx:Ta microbolometers could operate at a higher operating temperature range. The temperature coefficient of resistance (TCR) and the resistivity of the VOx:Ta (Ta content of 7.63%) films measured by four point probe measurement in heating system were −3.47%/K and 9.32 Ω-cm, respectively. The Ta-doped VOx microbolometer revealed a higher responsivity of 341 kV/W compared with 106 kV/W of the undoped VOx microbolometer.

In this paper, we have proposed an antireflection coating multi-layers of SiO 2 /Si 3 N 4 on silicon window, suitable for the infrared range of 8∼12 µm. The 4-layers coating (2-periods of SiO 2 /Si 3 N 4 ) with optimized thicknesses was designed using Essential Macleod program developed from Thin Film Center Inc. Based on the proposed long-wavelength infrared silicon-based window by simulation, the samples were also fabricated by physical vapor deposition technique to characterize and achieve the best possible agreement by FTIR spectroscopy. It was found that, in the wavelength range of 8∼12 µm, the average transmittance of the double-side coated sample increases by about 39% compared to uncoated silicon window and its maximum reaches about 98% at 9 µm.

This paper focuses on the high energy proton irradiation effect of InAs/GaAs multilayers quantum-dot (QD) wafer and photodetector. With high energy proton path simulation, the releases of proton energy and trap distribution in QD multilayers are predicted well. Treated by 1 and 3 MeV protons, all protons almost penetrate the multilayers of QD structures and stop deeply in GaAs substrate. InAs QD multilayer structures/Infrared photodetector have been irradiated by protons with different energies (1 and 3 MeV) and doses (1 × 10 9 ∼ 1 × 10 13 protons/cm 2 ). The photoluminescence (PL) and photoresponsivity (PR) spectrum of samples were measured and discussed with as grown and post irradiation.

The ten stacked self-assembled InAs/GaAs quantum dot infrared photodetectors (QDIP) with different Al/sub 0.3/Ga/sub 0.7/As barrier widths and growth temperatures were prepared. Asymmetric current-voltage (I-V) characteristics and 2/spl sim/7.5 /spl mu/m detection window were observed. Peak responsivity of 84 mA/W at -0.4 V and peak specific detectivity of 2.5/spl times/10/sup 9/ cm-Hz/sup 1/2//W at zero bias were observed at 50 K. The characteristics of polarization insensitivity over the incident light and the high background photocurrent suggest that the self-assembled QDIP can be operated at higher temperature (/spl sim/250 K) under normal incidence condition in contrast to quantum well infrared photodetector (QWIP).

I – V characteristics of the unpassivated InAs p–i–n diodes with various i-layer thickness have been systematically studied. At the same reverse bias of −0.5 V, the reverse current density is −0.83 and −0.18 A/cm 2 for the p–n diodes and p–i–n diodes with a 0.72-μm-thick i-layer, respectively. It is obvious that the surface shunt and bulk leakage current are dramatically decreased owing to increasing of the i-layer thickness between p and n layers of InAs p–n junction. Meanwhile, an odd current–temperature behavior; the reverse-bias current decreases with increasing temperature, has been observed in the InAs p–i–n photodetector with a 0.72-μm-thick i-layer. Below 90 K, the photocurrent generated by the background thermal radiation should dominate the I – V characteristics of the p–i–n diode and the photocurrent increases a little as temperature drops due to the improvement of minority carrier diffusion length.

The effect of temperature on the self-assembled InAs quantum dots (QDs) grown on GaAs substrate under arsenic shutter closed condition has been studied. From atomic force microscopy (AFM), it was found that the size of InAs dots exhibited a transition from single-sized uniformly distributed quantum dot (QD) at a growth temperature of 490°C to two groups of different sizes QDs at 510°C. Since the desorption rate of In atoms from the substrate surface is very high at 510°C, a growth model is proposed that attributes the larger sized QDs to the enhanced capture of desorbed In atoms by a local random protrusion which initiates a regenerative capture and growth process and leads to explosive growth.

In this letter, a 256/spl times/256 midwavelength infrared focal plane array (FPA) based on 30-period InAs-GaAs quantum-dot infrared photodetectors (QDIPs) is fabricated. The demonstrated original real-time nonuniformity corrected thermal images of hot soldering iron head with 30-Hz frame rate for the FPA are observed. Without additional light-coupling scheme, the QDIP FPA module is first operated at temperatures higher than 135 K under normal-incident condition with a 30/spl deg/ field of view and f/2 optics. For single device performances, a similar QDIP device with a 30-period InAs-GaAs QD structure is fabricated under the same processing procedure. High specific detectivity D/sup */ 1.5/spl times/10/sup 10/ cm/spl middot/Hz/sup 1/2//W and low noise current density 5.3/spl times/10/sup -13/ A/Hz/sup 1/2/ at applied voltage 0.3 V are observed.

The study is to demonstrate a dual-band infrared images based on two stacked InGaAs and GaAs-capped InAs QDIP structure, with the use of nano-scale Al2O3 surface passivated layer by ALD system deposited to decrease the device shot noise and boost the operation temperature of the thermal imaging FPA to 180 K.

A ten-stacked self-assembled InAs/GaAs quantum-dot infrared photodetector operated in the 2.5–7 μm range by photovoltaic and photoconductive mixed-mode near-room-temperature operation (⩾250 K) was demonstrated. The specific peak detectivity D* is 2.4×108 cm Hz1/2/W at 250 K. The use of high-band-gap Al0.3Ga0.7As barriers at both sides of the InAs quantum-dot structure and the long carrier recombination time are the key factors responsible for its near-room-temperature operation.

Electronic and optical properties of ideal and realistic quantum dots (QDs) are extensively studied and derived for the recent decade. Strain caused by the differences of the lattice constants of dot and wetting, barrier materials are decisive for both the self-assembly mechanisms and the electro-optical properties. This paper is mainly investigated for 3-dimensional (3D) electrical wave-functions and eigen-levels of multiple InAs/In(Ga)As self-assembled QDs matrix embedded in GaAs spacing layer incorporated with the three-dimensional (3D) Schrodinger equation and solved by using numerical finite element method (FEM) and PC-based dual-core CPU hardware. In this study, we will compare the samples with free and GaAs spacing layers of different thickness to investigate the influences on vertically coupled probability of density wave- functions. The spatially 3-dimensional ground-state wave- functions (|Psi|2) of 3-stacked InAs/InGaAs QD matrix with free GaAs spacing layer show the vertically strong coupled wave- functions are clarified to be demonstrated which will enhance the electrical propagated probability between vertically adjacent QD layers. And the vertically decoupled wave-functions (|Psi|2) are observed until the thickness of GaAs spacing layers are thicker than 2 nm.

For propose of achieving the high coherent quantum dots or the expected spectral emission, we have proposed the epitaxial method solved by using self-organized grown on the In x Ga 1-x As relaxed layer and the mis-orientated GaAs substrates. In this study, using extra slow growth rate of 0.075ML/sec to grow the quantum dot matrix under the temperature of 500°C by the general Riber 32P solid-source MBE system, the high surface density and uniformity in size of two-stacked of quantum dot (QD) matrix have been established. The temperature dependences of the full widths at half-maximum (FWHM) and the positions of photoluminescence (PL) bands are studied experimentally by adding In 0.1 Ga 0.9 As surfactant layer and using mis-orientated substrate, respectively. The 3-dimensional QD images using atomic force microscopy (AFM) well agree with the results of above mentioned. Therefore, a systematic estimate is given of the QD structures grown on different epitaxial conditions.

The InGaAs/InP P-I-N photodiodes are grown by a metal-organic chemical vapor deposition (MOCVD) with micro-effusion tubes of hydride carrier and reaction gases. Removing top InGaAs and using SiOx coverage on the photon absorbed area leads to enhance responsivity (~3 AAV) and quantum efficiency (>85%). And using Zn diffused to top ring InGaAs results in good ohmic contact region.

In this work, the 30 stacked InAs/GaAs quantum dot infrared photodetector (QDIP) structure was grown by solid-source molecular beam epitaxy technique and demonstrated with dual-band mid- (2.7~5.6μm) and long- (7.5~13.5μm) wavelength normal-incident detections without grating and passivated process for 256×256 FPA. The 256 ×256 QDIP FPA hybridized with snapshot-mode ROIC was mounted in a 68 pin leadless ceramic chip carrier which was put in the testing dewar with IR optical cold spectral filters of the 2.9~5.5μm and 6.5~14.5 μm for the dual-band IR detections, respectively. The testing scheme for thermal imaging uniformity of the InAs/GaAs QDIP focal plane array (FPA) has been proposed and calibrated using a plane-typed blackbody source of a high temperature of 373±1K and lower ambient temperature for the two-point temperature correction. The averaged of specific detectivity (D*) and operability of the QDIP FPA have reached 1.5×10 10 cm-Hz 1/2 /W and 99% at 80K, respectively. The dominant noise equivalent temperature differences (NEDT) of typical figure of merit for QDIP thermal imaging module operated under the temperature of 80K, device biases of -0.7 V and integration time of 32ms with infrared optics and two-point temperature correction (T L =R.T. and T H = 200 °C) are 1.065 K (mid-wavelength IR) and 131mK (long-wavelength IR), respectively. Meanwhile, it is worth to note that these are the first confirmation for dual-band detections of FPA from direct InAs quantum dots matrix embedded in GaAs heterostructure. In the future, the dual-band IR QDIP FPA will become one of the important candidates for hyper-spectral detection and thermal imaging fusion application.

Electronic and optical properties of ideal and real quantum dots (QDs) are extensively studied and derived for the recent decade. Strain caused by the differences of the lattice constants of dot and wetting, barrier materials are decisive for both the self-assembly mechanisms and the electro-optical properties. The research is mainly investigated for realizing the strain effects on the optical properties of InAs/GaAs self-assembled QDs embedded in GaAs barrier layer incorporated with the three-dimensional (3D) Schordinger equation and solved by using finite element method (FEM). From 3D QD geometrical profiles establishing by the spatially geometric equations, the confined electron and hole bandstructures on altering sized lens and pyramidal shape-like QDs with numerical calculations and strained heterostructure of the finite element approximations have been proposed. Applying the fast FEM models, it is demonstrated that the correspondence of ground, excited eigenstates, the probability of density function (|Ψ| 2 ) of the confined levels from the single InAs QD to a matrix of nine QDs to obtain the transition energy and coordinated absorption wavelength to be predicted and summarized clearly. Through calculating energy levels within the conduction and valence band edge confinement on the InAs/GaAs heterostructure with FEM to contradistinguish with corrected to optical transitions and linear absorption spectra can be achieved for verifying to being the specific wavelengths from photoluminescence (PL) and photoresponse (PR) measurements for quantum dot infrared photodetector. By fitting the energy differences among the subbands, the geometrical shape and size of QD can be predicted. Inducting the tendency from single QD to the matrix of 9 QDs, the step-wise bands have been obtained being some regularity clearly. And from the transmission electron microscope (TEM) measurement, the dominant sizes of QDs in the really grown wafer remain the consistent with the numerical analyses applied in 3D QD profile that is interpreted using spatially geometric equations.

The quantum dot (QD) resonant tunneling diode (RTD) with Al/sub x/Ga/sub 1-x/As double-barriers has been investigated under operating large temperature ranges. A superior temperature-stability of peak-to-valley current ratio (PVR) is demonstrated. The electrons of resonant tunneling transport via nm-scale InAs quantum dots buried in GaAs spacer layers bounded by a pair of very thin Al/sub 0.3/Ga/sub 0.7/As barriers.

We present results concerning the influence of organometrallic vapro phase epitaxy (OMVPE) grwoth paramters under ultra low V/III ratio on the surface morphology and temperature-dependent photoluminescence. Due to Indium segregation inteh 2D InAs wetting layers and accumulation from multi-atomic step edge on (001) 2° off toward (111) n-type GaAs substrate, self-assembled InAs quatnum dot formation takes pace aroudn or above 2D InAs islands while ~ one monolayer of InAs is regularly grown on GaAs substrate. It is attributed that the desorbed Indium Recaptured and nucleated effect on edge along (110)-orientation of GaAs substrate.

The InAs/GaAs quantum dot (QD) edge light emitting diode (LED) emitting at a wavelength of 1 /spl mu/m has been fabricated which exhibits very small wavelength shift of 0.22 nm/K and the full width at half maximum (FWHM) broadening shift of 0.04 nm/K. Detailed temperature characteristics over a range from 20 to 300 K are presented.

Self-assembled quantum dot has been realized in different optical-electric material systems and different growth techniques using Stranski-Krastanow growth mode [1]. The optical properties of quantum dots are of physical interest due to the experimental investigation. The theoretical predictions of quantum dot device have been well verified [2]. In the article, we studied the temperature dependent electrical and optical properties [2,3] of quantum dot under normal incidence. From the measurement results, we found the three-dimensional confinement of QD structure and the inter- confined state [4-6].

In this letter, the effect of extraordinary transmission of periodic metal hole arrays is directly integrated into the quantum dot infrared photodetector with broadband response. It is found that the detector response is strongly modulated by the extraordinary transmission from the excitation of surface plasmon.

The temperature-dependent capacitance–voltage (C–V) characteristics of two stacked InAs/GaAs quantum dot p–i–n diode were investigated. The capacitance discontinuities observed are attributed to charge storage in the InAs quantum dots. The average storage electrons at each InAs quantum dot thus obtained are two and three electrons at room temperature and at temperature below 100 K, respectively. In the intermediate temperature range from 100 to 250 K, fractional charge occupation is observed in each dot. When the C–V measurement frequency is lowered from 800 to 80 kHz, the capacitance turns into a negative value under low biases which indicates the dominance of the inductance at lower frequency.