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In nanostructure like quantum dots (QDs) embedded in the spacing layer with high energy barrier, where electrons are three-dimensionally confined into nanometer-scale semiconductor structures, the novel physical characteristics are expected to emerge. The novel properties would greatly improve semiconductor device performance. Optoelectronic devices with quantum dot heterostructure like quantum dot infrared photodetector (QDIP) have already been proposed in the recent years. When QDs are incorporated into the layered structure of a semiconductor for optoelectronic device applications, electrical control is critical to the operation of device. It is desirable that both an electric field can be applied to change physical properties of the QDs embedded in the spacing layers i.e., the active region of the device and that the photo-induced carriers can be excited and transited to generate the photocurrent. In this chapter, The pseudopotential model of using multiple-quantumdot (MQD) structures for detect infrared radiation can be explained by exploiting the basic principles of quantum mechanics, with the uniform and isotropic strain-induced potential to well simulate the electronic properties of InAs/In(Ga)As QDIP active region by finite element method (FEM). The vertically coupled and decoupled wave-functions of electrons on MQD with dependences of thickness of spacing layers are also calculated by means of the FEM. The method is ideally suited for numerical analysis by computer. The typical and particular QDIP structure are involved and introduced in this section. Here, the outstanding performance of the QDIP which has emerged as a potential alternative to QWIPs would be proposed. The motivation for interest in QDIPs is rooted in two characteristics of quantum dots. The first is that QDIPs are sensitive to normal-incident infrared radiation, a consequence of the 3-D confinement of electrons in the quantum dots. The other attribute is the weak thermionic coupling between the ground state and excited states. This should result in lower thermal excitation and, thus, lower dark current and higher operating temperature. The concomitant increase in the lifetimes of excited carriers should enable higher responsivities as carriers have more time to escape and contribute to the 13

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.

In this study, we study a heat transfer model, with the surface of the microbolometer device receiving radiation from blackbody constructed using a COMSOL Multiphysics simulator. We have proposed three kinds of L-type 2-leg and 4-leg with the pixel pitch of 35 &mu, m based on vanadium oxide absorbent membrane sandwiched with top passivated and bottom Si3N4 supporting films, respectively. Under the blackbody radiation, the surface temperature changes and distributions of these samples are simulated and analyzed in detail. The trend of change of the temperature dependent resistance of the four kinds of bolometer devices using the proposed heat transfer model is consistent with the actual results of the change of resistance of 4 samples irradiated with 325 K blackbody located in the front distance of 5 cm. In this paper, &Delta, T indicates the averaged differences of the top temperature on the suspended membrane and the lowest temperature on the post of legs of the microbolometers. It is shown that &Delta, T &asymp, 17 mK is larger in nominal 2-leg microbolometer device than that of 4-leg one and of 2-leg with 2 &mu, m &times, 2 &mu, m central square hole and two 7.5 &mu, m slits in suspended films. Additionally, only &Delta, 5 mK with 4-leg microbolometer device under the same radiated energy of 325 K blackbody results from the larger total thermal conductance.

In this research, we have proposed the analytical modeling of the stress and surface temperature distribution on the microbolometer pixel is significant for optimizing its performance. Therefore, this study investigates the stress including thermo distributive characteristics of a microbolometer pixel which is considered with the effects of intrinsic stress, joule heating and incoming IR energy on the microbolometer device structure.

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.

GaSb/GaAs quantum dots (QDs) and quantum rings (QRs) are investigated. By using periodical growth interrupts, precise coverage control can be achieved for GaSb QD growth by using a single Ga source. With direct As irradiation to the substrate surface during the post soaking time, the soaking time can be effectively reduced while full ring morphologies and room-temperature QR luminescence can still be obtained by using this method.

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 influences of the low V/III ratio on the surface morphologies and temperature-dependent photoluminescence spectrum of InAs-GaAs quantum dots (QDs) prepared by organometallic vapor phase epitaxy are investigated. Due to the accumulation of In adatoms at the multiatomic step edge on [001] 2/sup 0/ off toward an [111] n-type GaAs substrate, InAs island growth with /spl sim/1 ML coverage takes place prior to the InAs QD formation. With increasing InAs coverage, self-assembled InAs QDs are observed near the InAs islands, which is attributed to the recapture of desorbed In atoms nucleating with supplied As atoms on the edge along [11~0]-orientation of the GaAs substrate.

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).

In this paper, figures of merit describing the performances of infrared (IR) bolometer sensor such as thermal response time (a#x03C4;), responsivity, detectivity (D), noise equivalent power (NEP) and noise equivalent temperature difference (NETD) are estimated using numerical simulations. The proposed model is based on the analytical formulas from Frank Niklaus, et.al. Using this model, we have evaluated the performance of two-legged, uncooled infrared bolometer sensor with 52×52 a#x03BC;m2 and 35×35 a#x03BC;m2 pixel-pitch size. The bolometer sensors were fabricated by Institut National d'Optique (INO), Canada and National Chung-Shan Institute Science of Technology (NCSIST), Taiwan. Test structures including uncooled vanadium oxide bolometer FPAs were fabricated at INO to verify the agreement between the simulated and experimental data. The performance model was used at NCSIST to evaluate the improvements on design and fabrication of bolometer FPAs with pixel pitch varying form 35 a#x03BC;m to 52 a#x03BC;m.

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.

An unpassivated InAs p-i-n photodetector with excellent performance at room temperature was demonstrated. The zero-bias resistance area products of the diode with 720-nm thick i-layer are 8.1 /spl Omega/-cm/sup 2/ at room temperature and as high as 1.3 M /spl Omega/-cm/sup 2/ at 77 K. At 77 K, the diode exhibits a breakdown voltage exceeding 13 V. When tested under a 500 K blackbody source, the measured detectivity limited by Johnson noise is 1.2/spl times/10/sup 10/ cm-Hz/sup 1/2 //W at room temperature and 8.1/spl times/10/sup 11/ cm-Hz/sup 1/2 //W at 77 K. To our knowledge, this is the best data for a room temperature infrared detector.

This paper proposes dual-mode buffer direct injection (BDI) and direct injection (DI) readout circuit design. The DI readout circuit has the advantage of being a simple circuit, requiring a small layout area, and low power consumption. The internal resistance of the photodetector will affect the photocurrent injection efficiency. We used a buffer amplifier to design the BDI readout circuit since it would reduce the input impedance and raise the injection efficiency. This paper will discuss and analyze the power consumption, injection efficiency, layout area, and circuit noise. The circuit is simulated using a TSMC 0.35 um Mixed Signal 2P4M CMOS 5 V process. The dimension of the pixel area is 30×30 μm. We have designed a 10×8 array for the readout circuit of the interlaced columns. The input current ranges from 1 nA to 10 nA, when the measurement current is 10 pA to 10 nA. The integration time was varied. The circuit output swing was 2 V. The total root mean square noise voltage was 4.84 mV. The signal to noise ratio was 52 dB, and the full chip circuit power consumption was 9.94 mW.

We report on analysis and comparison of the dark current characteristics between InAs p-n and p-i-n diodes at the temperature range from 30 to 300 K. The situation that the dark current is completely due to the bulk instead of the surface leakage is made sure by passivation treatment. The experimental results agree well with a tunnel diode model in which the p-n and p-i-n diodes are described, respectively, with a linear electrical field and a constant electrical field. The diffusion current in our diodes is dominated by the electron diffusion in the p-type material. Through this model and detailed analysis, we conclude that the tunneling current can be suppressed with an intrinsic layer and a low n-type doping density while the diffusion current can be decreased with a high p-type doping density. The advantage of the p-i-n structure is not only to cut down the tunneling current but also to increase the uniformity. In terms of this model, a new p-i-n diode is designed to dramatically increase its zero-bias resistance area product and improve the detector performance. (C) 1996 American Institute of Physics.

This paper discusses a capacitor transimpedance amplifier (CTIA) designed for an infrared readout circuit. The CTIA has better gain control, high dynamic range, a stability bias point and low impedance. It applies a short-wave detector and small current source because input impedance is very small in an amplifier feedback mechanism. This research on a capacitor transimpedance amplifier (CTIA) is designed for an infrared readout circuit. It is designed, simulated and laid out using the TSMC 0.35um 2P4M CMOS 5V process. The clock rate operates at 3MHz. Layout area is 30umX30um and the array size is 20X16. The simulation current sets 0.01nA~1.3nA. The output swing is 2.8V and power consumption is 10.1 mW according to the measurement results.

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.

This paper presents the readout circuit based on Direct Injection (DI) and Capacitive Transimpedance Amplifier (CTIA). The hybrid type of CTIA and DI was adopted as the pixel circuit's design in this paper. The two different structures were combined into unit pixels, and each pixel has two modes of readout. Furthermore, the chip was produced with TSMC 2P4M 5V technology, and the array size is 10×8. The output swing is 2.1V and power consumption is 9.4 mW, according to measurement results. The Layout area is 40um × 40um, and the two modes are selected by an external pin. The dual mode structure enables single- and dual-band infrared sensors. The readout chip can operate in 2kHz ∼ 6MHz, and the input photocurrent range is 1pA ∼ 50nA, depending on integration time; thus, it can be suitable for various detectors.

This study proposes a solution for an excessive dark current by a sharing capacitor, which avoids output signal distortion due to integration voltage saturation. Integration capacitance can be changed by adding a switch in the pixel circuit, which will increase the capacitance by two times the original. This circuit also provides output functions of either single-band or dual-band by switching to different sensor. This integrated readout circuit design adopts the TSMC 0.35um 2P4M CMOS 5V process, run on a 5V power supply and operated at a 3MHz clock rate. The dual-band pixel circuit uses an interlace structure, the pixel circuit areas of the two wavelengths are both 30um x 30um. The mid-wave and long-wave sensor currents are from 1nA to 2nA and 6nA to 8nA, respectively, and output swing is 2.8V.

This paper proposes two kinds of readout integrated circuits for column and row interlaced dual-band infrared detectors. The experiments were simulated using TSMC 0.35μm Mixed Signal 2P4M CMOS process and operated at 3MHz clock rate. The pixel dimensions for two kinds of readout integrated circuits were also 30×30μm. The mid-wave and long-wave sense current was set from 1nA to 2nA and 6nA to 8nA, respectively. We designed a 40x16 array for the columns interlace readout circuit. The output voltage swing was 2.8V. The frame rate was 4.68kFPS. The total power consumption was less than 17.6mW. We also designed a 20x32 array for the row interlace readout circuit. The output voltage swing was 2.8V. The frame rate was 2.67kFPS. The total power consumption was less than 11.4mW. The power consumption increased when the column interlace frame rate reached the row interlace frame rate. The row interlace can decrease the layout area by sharing the column stage circuit, but the frame rate will drop to half of the single band frame rate.

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.

This paper discusses about a readout circuit for Dual-Band Quantum Well Infrared Photo-detectors (DBQWIP) interlaced focal plane array infrared image system. In this research, we will present the study of modified dark-current cancellation circuit. The sensing photo-current from 1nA to 10nA of long-wave infrared signal, mid-wave infrared photo-current is about 100pA to 1nA, the dark current is set up to 100nA. The area of unit pixel is 30×30μm 2 . The 8×6 focal-plane array is designed by using TSMC 0.35μm 2P4M CMOS process. This work has 3.3V power supply and readouts data at 2.5MHz clock rate. The simulated output voltage range of LWIR and MWIR photo-current are 0.95v and 0.76v, respectively.

This paper discussed about a readout circuit for Quantum Dot Infrared Photodetector (QDIP) Focal-Plane-Array (FPA) imaging system. The readout circuit employed a modified regulated cascode circuit to stabilize the bias of QDIP. The readout circuit consisted of in-pixel dark current cancellation circuit, sensed current integration and in-pixel switch integration capacitor. The chip worked at 5V power supply and operated at 1MHz clock rate. Output voltage ranging from 2 volt to 4 volt was generated when the sensing current from 10nA to 100nA, the dark current was set up to 100nA. The total power consumption was less than 3.3 mW. The dimension of unit pixel was 30×30μm and the integration capacitance was about 0.24pF. The 8×8 pixels array readout circuit of in-pixel variable integration capacitors was implemented by using TSMC 0.35μm Mixed Signal 2P4M CMOS process.

A feedback power control system includes: a multiplying unit receiving work voltage corresponding to the voltage drop in an electrical component and feedback voltage corresponding to the work current flowing through the electrical component, with outputting a measurement voltage corresponding to the power consumed by the electrical component, having a value equal to the product of the work voltage and feedback voltage. The control unit receives the measurement voltage from the multiplying unit and a reference voltage, and outputs a control voltage corresponding to the difference in voltage between the measurement voltage and the reference voltage. The regulating unit provides the feedback voltage to the multiplying unit and includes an amplifier that receives the feedback voltage from the electrical component. In this way, we can adjust the current flowing through the electrical component when the electrical component voltages vary with temperature. Reducing the power dependence of the electrical component to the temperature that compensates the temperature is our purpose. Both the automatic constant current and automatic power control can be provided by a single system.

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.

This paper mainly focuses on the simulation for temperature-dependent Distributed Bragg Reflector (DBR) of 850nm vertical cavity surface emitting laser (VCSEL) with Transmission Matrix (TMM), Matrix Calculating Methods (MCM) and Macleod Model and performance for comparison with proton-implant/oxide confined process on VCSEL. Using well-developed temperature-dependent DBR-reflectivity solver with Mathcad simulator, we have successfully compared the Macleod Model simulator with theoretical self-developed solution based on the Transmission Matrix (TMM), Matrix Calculating Methods (MCM) and find very good agreement with previous results while accounting for influences of conjugated part of refractive index and graded Al compositions of DBR materials. Moreover, optoelectronic performance of Proton-Implant/Oxide Confined 850nm VCSEL have been demonstrated on this paper using temperature-dependent power output, voltage/injection current, transverse operating wavelengths, optical spectral characteristics, slope efficiency and transverse optical modes with an approximated Marcatili's method extracted and measurement from systematically measuring experiments. Through adequate and precise LD device design and processes, we have proposed the high performance single-mode proton implanted in contrast to the oxide confined 850 nm VCSEL. Under nominal temperature-variety and keeping operating temperature of 30°C,the threshold voltage, injecting current, peak-wavelength and differential resistance of the proton implanted VCSEL with the optical aperture in the dimension of 10 mm are 1.8 V, 3.2 mA, 851 nm and 36.8 ohm, respectively.

The vertical cavity surface emitting laser (VCSEL) based on graded distributed Bragg reflectors (DBR) consisted of a top mirror of 20 pairs of AlxGa1-xAs/AlyGa1-yAs (x=0~0.9, y=0~0.12) quarter-wave stacks and a bottom mirror of 34 pairs of AlyGa1-yAs/AlxGa1-xAs quarter-wave stacks has been demonstrated. Using two proposed transfer matrix methods, the simulation of DBR reflectivity depending on temperature refractive index of AlxGa1-xAs and AlyGa1-yAs are discussed and investigated. The simulation results could be achieved to well predicted the DBR performance under operating temperature variances, i.e., the temperature on varying reflectivity and full width half maximum (FWHM), wavelength stop-band shifts of the laser reflector, where using the multi-layer films evolution software of essential Macleod and modified transfer matrix method, respectively. Under our simulation, assuming the physically VCSEL device feature such as the linear grading DBR structure sandwiched with a n-type GaAs substrate and air films, we have systematically studied the temperature effects on the key parameters of top and bottom DBR schemes. In contrast with the temperature dependent DBR on the 850nm-VCSEL characteristics simulated with the above two transfer methods, the temperature varying spectra of VCSEL are agreed with the our simulated results presented in this paper. Also the temperature dependent model of DBR based on refractive index of graded multi-AlxGa1-xAs/ AlyGa1-yAs has been proposed. So, a series of optoelectronic measurements experimentally confirm our results again. The maximum reflectivity of the top and bottom DBRs are 96.4 and 99.98%, respectively. The central wavelengths of the bandwidth spectra in the top and bottom DBR are same. i.e., 840nm. These results can be obtained the criteria for the high performance VCSEL design. The far-field patterns of transverse electromagnetic fields confined in

The noise characteristics associated with dark current, photoconductive gain (PC), capture probability in doped InAs dots embedded in In 0.1 Ga 0.9 As/GaAs spacer layer have been proposed. The photoconductive and photovoltaic behaviors of the InAs/GaAs quantum dot infrared photodetector (QDIP) from the intersubband transition measurements are also clearly observed. Through noise measurement in dynamic signal analyzer (HP35670A) 1 , the electronic bandpass filter frequencies are set up ranging from 3 to 10 KHz in a low noise current preamplifier (SR570) 2 . The lock-in amplifier (SR830) 3 can be also used to measure and calibrate the noise density by means of the mean average deviation (MAD) contrast with noise spectra from HP35670A. The InAs/GaAs QDIP studied in this work belongs to n + -n-n + structure with the top and free blocking barrier layers. It is observed that the owing blocking layer of QDIP not only suppress dark current successfully but also probably reduce the photocurrent 4-6 . By systematically optoelectronic measurements and simulations, the modified model of noise current, photoconductive gain, and capture probability in the quantum devices have been proposed. It is shown that photoconductive gain is almost independent of bias under the lower bias, then increasing exponentially under higher bias and below the temperature of 80K. In contrast to quantum well infrared photodetector (QWIP), a higher photoconductive gain of the quantum dot infrared photodetector has been demonstrated and attributed to the longer lifetimes of excited carriers in quantum dots 7-10 . At 80K, a photoconductive gain of tens of thousand is shown in the regions of higher biases. It is clear to note that the highest detectivity of the QDIP surprisingly approach to 3.0×10 12 cmHz 1/2 /W at -0.6V under measured temperature 20 K. Under 80K, the average D* is obtained ~10 10 cmHz 1/2 /W. To our knowledge, this is the one of highest D* data in the world.

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].

Quantum dot infrared photodetectors (QDIPs) have been shown to be a key technology in broad infrared wavelength (3–12 µm) detection due to their potential for normal incidence operation, low dark current density and higher temperature operation. In our research, we have been investigating infrared detectors based on intersubband transitions in a novel InAs/In 0.15 Ga 0.85 As quantum dots-in-well (DWELL) and normal GaAs-capped InAs quantum dot heterostructures. The study is to demonstrate a dual-band infrared image based on two stacked InGaAs and GaAs- capped InAs QDIP structure, with the use of nano-scale Al 2 O 3 surface passivated layer by atomic layer deposition (ALD) system deposited to decrease the device shot noise and boost the operation temperature of the thermal imaging FPA to 180 K. It is worth to mention the specific detectivities (D*) of test device passivated with Al 2 O 3 measured under 80 K and Vb = –3.3 V for mid-wavelength detection is as high as 2.1 × 10 11 cmHz 1/2 /W. By a two-step selective backside etching process, the uncorrected non-uniformity of NEDT is lowered to 6.7%. It reveals the high uniformity of infrared image taken from QWIP FPA with this proposed process is comparable to the conventional one with the mixture of wet- and dry-etching ICP-RIE.

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.

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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.

The current leakages of InAs photodiodes have been systematically studied by adding undoped layers having thicknesses of 0, 0.30, and 0.72 μm between the p–n junction. At reverse bias V=−0.5 V, the dark currents of the InAs p–i–n diodes with undoped layer thicknesses of 0, 0.30, and 0.72 μm are about 5×10−6, 7×10−8, and 1×10−10 A, respectively, at 77 K. The leakage current of the InAs p–n diode was successfully reduced by adding 0.72-μm-thick undoped layer between the p–n junction.