Simulation of avalanche multiplication of electrons in photodetectors with blocked hopping conduction

The avalanche electron multiplication in a silicon structure with blocked hopping conduction is simulated for the photon-counting mode. The acceleration of an electron in an electric field that is linearly dependent on the coordinate, the elastic scattering of electrons by longitudinal acoustic phonons, the inelastic scattering of electrons by intervalley phonons, and the ionization of impurity centers are taken into account when considering the motion of an electron. A simple algorithm making it possible to calculate directly the coordinates of all ionized centers in an avalanche and the probability of N electrons leaving the avalanche if a single electron has entered the multiplication region is suggested. It is shown that this probability is at its maximum in the vicinity of 〈N〉 (the mean value of the leaving-probability function), which is consistent with experimental data.     

Current-voltage characteristics of Si:As-based photodetectors with blocked hopping conductivity

The results of an experimental investigation of the current-voltage characteristics of Si:As-based structures with blocked hopping conductivity are reported. The behavior of the dark current in the temperature range T=7–25 K with bias voltages from −4 to +4 V is analyzed and views about the mechanisms of dark-current flow are presented. Recommendations are developed for choosing the bias voltage on the structures for optimal operation as an IR photodetector. Fiz. Tekh. Poluprovodn. 33, 614–618 (May 1999)     

Current-voltage characteristics of Si:As blocked impurity band photodetectors with hopping conductivity (BIB-II)

The current-voltage characteristics of Si:As blocked impurity band (BIB) structures are investigated. The behavior of the dark current in the temperature range 4.2–25 K and in the range of bias voltages −3 to +3 V is analyzed. It is shown that the main features of the I-V characteristics are governed by the thermal-field injection of charge carriers from the contacts to the BIB structure. The details of the I-V characteristics for bias voltages of both polarities are attributed to generation-recombination processes between the conduction band and the impurity band of the N ⁺ photoconductive layer. It is established that the blocking layer can accumulate charge of both signs, influencing the formation of the dark I-V characteristics. Fiz. Tekh. Poluprovodn. 33, 1005–1009 (August 1999)     

Injection currents in silicon structures with blocked hopping conduction

It is shown that injection currents in structures with blocked hopping conduction (the so-called BIB structures) may be interpreted as Richardson thermionic currents flowing through potential barriers. The latter are governed by the electron chemical potential in the N ⁺⁺-N ⁺ (N ⁺⁺-I) regions. It is also shown that measurement of the injection potential is a convenient method for determining the degree of compensation in silicon structures with “ohmic” contacts.     

Light coupling characteristics of corrugated quantum-well infrared photodetectors

Corrugated quantum-well infrared photodetectors (C-QWIPs) offer simple detector architectures for large-format infrared focal plane arrays (FPAs). The detector relies on inclined sidewalls to couple normal incident light into the absorbing material. Based on a simplified geometrical-optics (GO) model, this light coupling scheme is expected to be effective with little wavelength dependence. In this work, we apply the modal transmission-line (MTL) modeling technique to study in detail its light coupling characteristics and compare the results with the GO model and experimental data. We find that the results of the GO model agree reasonably well with those of the rigorous MTL model for corrugations with metal cover, and both modeling procedures are consistent with experimental data. In particular, both models predict similar increase in the quantum efficiency /spl eta/ with the size of the corrugations, and both indicate similar limiting /spl eta/ when the corrugation becomes very large. For linear corrugations with thick substrates, the maximum /spl eta/ is about 30%. On the other hand, there are also significant differences between the two models when the effects of phase coherence are important. Since the phase of the radiation is taken into account in the MTL formalism but not in the GO formalism, the MTL model is more generally applicable and is more capable of explaining different detector characteristics. For example, it predicts a smaller /spl eta/ for air or epoxy-covered C-QWIPs because of finite optical transmission through the sharp corners in the corrugations, and it indicates an oscillatory function of /spl eta/ because of the existence of optical fringes. It also reveals the wavelength dependence of the coupling, which becomes more pronounced as the thickness of the substrate layer is reduced.     

Refined model for the current-voltage characteristics of quantum-well infrared photodetectors

The temperature dependences of the dark current of quantum-well infrared photodetectors are investigated experimentally. It is established that the pre-exponential factor in the analytical expression for the photodetector current-voltage characteristics varies linearly with temperature. On the basis of the results obtained, it is suggested that the temperature dependence of the photodetector??s dark current is determined by the thermal excitation of charge carriers to a band characterized by a two-dimensional density of states. In the context of this suggestion, a refined model for the current-voltage characteristics is proposed. The model takes into account the thermal generation of charge carriers in a band with a two-dimensional density of states and the electric field dependence of the thermal activation energy for the quantum-well ground state and of the drift velocity of the carriers in the barrier conduction band.     

量子级联红外探测器

半导体基中远红外探测器在成像、传感、国家安全以及国防领域具有广泛的应用背景.目前,在这个领域最主流的技术之一是量子阱红外探测器( QWIPs).传统的量子阱红外探测器往往存在较大的暗电流和较低的工作温度等限制.量子级联探测器( QCDs)是一种新型的光伏型量子阱红外探测器.其工作原理基于电子吸收光子后在量子阱的子带间跃...     

Process modeling of HgCdTe infrared photodetectors

A physically based process model for simulating the fabrication of HgCdTe photodiodes has been developed. The models included in the simulator are based on atomic level mechanisms governing the interaction of point defects, extended defects, and dopants. The core of the simulator is a set of coupled partial differential equations for point defect/dopant diffusion. The simulator models the processing of n on p, ion implanted homojunction long wavelength infrared photodiodes. Because the models are physically based, the simulator can be used with other materials and device architectures if properly calibrated. The simulator includes modules for annealing and boundary conditions, ion implantation, and reactive ion etching and can produce both one and two dimensional dopant and defect profiles. Coupled with device and performance simulators, it forms a powerful tool for design and optimization of HgCdTe photodiodes. The simulator operates in a client/server mode in an intranet or internet environment. A web browser interface provides a user friendly front end for inputting processing parameters and outputting simulation results.     

Novel MIS Ge-Si quantum-dot infrared photodetectors

The metal-insulator-semiconductor (MIS) Ge-Si quantum-dot infrared photodetectors (QDIPs) are successfully demonstrated. Using oxynitride as gate dielectric instead of oxide, the operating temperature reaches 140 and 200 K for 3-10 and 2-3 /spl mu/m detection, respectively. From the photoluminescence spectrum, the quantum-dot structures are responsible for the 2-3 /spl mu/m response with high operation temperature, and the wetting layer structures may be responsible for the 3-10 /spl mu/m response. This novel MIS Ge-Si QDIP can increase the functionality of Si chip such as noncontact temperature sensing and is compatible with ultra-large scale integration technology.     

High responsivity InP-InGaAs quantum-well infrared photodetectors: characteristics and focal plane array performance

We report the detailed characteristics of long-wavelength infrared InP-In/sub 0.53/Ga/sub 0.47/As quantum-well infrared photodetectors (QWIPs) and 640/spl times/512 focal plane array (FPA) grown by molecular beam epitaxy. For reliable assessment of the detector performance, characterization was performed on test detectors of the same size and structure with the FPA pixels. Al/sub 0.27/Ga/sub 0.73/As-GaAs QWIPs with similar spectral response (/spl lambda//sub p/=/spl sim/7.8 /spl mu/m) were also fabricated and characterized for comparison. InP-InGaAs QWIPs (20-period) yielded quantum efficiency-gain product as high as 0.46 under -3-V bias with a 77-K peak detectivity above 1/spl times/10/sup 10/ cm/spl middot/Hz/sup 1/2//W. At 70 K, the detector performance is background limited with f/2 aperture up to /spl sim/ 3-V bias where the peak responsivity (2.9 A/W) is an order of magnitude higher than that of the AlGaAs-GaAs QWIP. The results show that impact ionization in similar InP-InGaAs QWIPs does not start until the average electric-field reaches /spl sim/25 kV/cm, and the detectivity remains high under moderately large bias, which yields high responsivity due to large photoconductive gain. The InP-InGaAs QWIP FPA offers reasonably low noise equivalent temperature difference (NETD) even with very short integration times (/spl tau/).70 K NETD values of the FPA with f/1.5 optics are 36 and 64 mK under bias voltages of -0.5 V (/spl tau/=11 ms) and -2 V (/spl tau/=650 /spl mu/s), respectively. The results clearly show the potential of InP-InGaAs QWIPs for thermal imaging applications requiring high responsivity and short integration times.     

A new approach for modeling of dark current characteristics of quantum wire infrared photodetectors

In order to study the dark current characteristics in a quantum wire infrared photodetector(QRIP),the average number of electrons in quantum wires(QRs) must be got,which is mostly too complicated.In this paper we give a simple formula to calculate the average number of carriers in a quantum wire(QR) that can be easily evaluated by mathematical softwares,and then we use this formula to study dark current characteristics of a quantum wire infrared photodetector(QRIP). 更多还原     

量子阱红外探测器最新进展

量子阱红外探测器(QWIP)自从20世纪80年代被验证后,得到了广泛积极的研究。基于Ⅲ-Ⅴ材料体系、器件工艺的成熟和自身的稳定性、响应带宽窄等特有的优势,QWIP成为对低成本、大面阵、双(多)色高精度探测有综合要求的第三代红外焦平面阵列(FPA)的重要发展方向。本文主要总结了国际QWIP器件的最新发展动态,并展望了其发展趋势。     

GaAs/Al0.3Ga0.7As 量子阱红外探测器光谱特性研究

采用金属有机物化学气相沉积法(MOCVD)生长GaAs/Al0.3Ga0.7As量子阱材料,制备300 m300 m台面,内电极压焊点面积为20 m20 m,外电极压焊点面积为80 m80 m单元量子阱器件两种。利用傅里叶光谱仪对1#,2#样品进行77K液氮温度光谱响应测试。实验结果显示1#,2#样品峰值响应波长分别为8.43 m,8.32 m,与根据薛定谔方程得到器件理论峰值波长8.5 m间误差分别为1.0%,2.1%。实验结果说明MOCVD技术可以满足QWIP生长制备工艺要求,且器件电极压焊点位置与面积大小对器件峰值波长影响不大,而对峰值电流有一定影响。     

国外红外光电探测器发展动态

主要综述三代红外光电探测器的材料体系与研究现状,以及分析红外光电探测器的未来发展趋势。首先,简述红外光电探测器及其三个发展阶段。然后,论述适于三代红外光电探测器发展的碲镉汞（HgCdTe）、量子阱光探测（QWIPs,quantum-well photodetectors）、二类应变超晶格（SLS,type-Ⅱ strained-layer superlattices）和量子点红外光探测（QDIPs,quantum dot IR photodetectors）四个材料体系,以及介绍它们在三代红外光电探测器方面的研究进展。最后,分析未来红外光电探测器的材料选择及发展趋势。     

Swept away [quantum-well infrared photodetectors]

The ultra high-speed capability of quantum-well infrared photodetectors (QWIPs) is well known, thanks to their intrinsic short carrier lifetime (/spl sim/5 ps). This obviously makes QWIPs well suited for high-speed and high-frequency applications. In the past, for thermal infrared imaging where devices are optimized to have the highest possible detectivity, the absorption quantum efficiency has been low (<10%). For high-speed applications where lasers are usually used, the most important parameter is the absorption efficiency. We show that high absorption (/spl sim/100%) can be easily achieved by simply changing some of the device parameters. We also review the experimental demonstrations of the high-speed capability. At present, QWIPs hold the unique position of having high-speed/-frequency capability and high absorption for the thermal infrared region. There are no competitive alternatives.     

Voltage-tunable dual-band infrared photodetectors with Si/SiGe metal-semiconductor-metal heterostructure

A simple and low-cost structure of voltage-tunable dual-band near-infrared photodetector (PD) has been proposed, in which the PDs were developed by using Si_0.8Ge_0.2/Si metal-semiconductor-metal (MSM) heterostructure. The Si_0.8Ge_0.2/Si layers were deposited by ultrahigh-vacuum chemical vapor deposition system and a transparent layer of indium-tin oxide (ITO) was used as a metal layer to enhance the entrance of photons. In this study, we found that only one band was detected with a peak wavelength located at 950 nm at zero applied bias. When bias was increased to 1 V, in contrast a dual-band was achieved, where two peak wavelengths were centered at 950- and 1150-nm. It is suggested that the two bands are the absorption of top-Si and bottom-Si_0.8Ge_0.2 layers, respectively. The spectra of Si bulk and Si_0.8Ge_0.2 layer were also measured to verify our results and relating mechanisms are explained here.     

High-frequency quantum-well infrared photodetectors measured bymicrowave-rectification technique

We explore the high-frequency capability of quantum-well infrared photodetectors using a microwave-rectification technique. We characterize a variety of devices with barrier thicknesses from 234 to 466 Å and number of wells from 4 to 32. Our packaged detectors have a relatively flat frequency response up to about 30 GHz. These experiments indicate that the intrinsic photoconductive lifetime for these devices in the high-biasing field regime is in the range of 5-6 ps     

Normal-incidence InAs self-assembled quantum-dot infrared photodetectors with a high detectivity

An InAs/AlGaAs quantum-dot infrared photodetector based on bound-to-bound intraband transitions in undoped InAs quantum dots is reported. AlGaAs blocking layers were employed to achieve low dark current. The photoresponse peaked at 6.2 /spl mu/m. At 77 K and -0.7 V bias, the responsivity was 14 mA/W and the detectivity, D*, was 10/sup 10/ cm/spl middot/Hz/sup 1/2//W.     

Waveguide infrared photodetectors on a silicon chip

A novel infrared (IR) photodetector structure is discussed. It represents a waveguide in which the core is a strained-layer GexSi1-x/Si superlattice (SLS) sandwiched between Si layers of a lower refractive index. Absorption of infrared radiation occurs in the core region due to interband electron transitions, and photogenerated carriers are collected in the Si cladding layers. Due to the recently discovered effect of bandgap narrowing by the strain in alloy layers the fundamental absorption threshold of the SLS is shifted to longer wavelengths, so that the detector can be operated in the range of silica-fiber transparency, 1.3-1.55 µm. The optimum SLS composition and thickness have been estimated from the known material properties and waveguide theory. The detector quantum efficiency grows with the optical path length, remaining consistent with the requirements of high-speed fiber-optical communications. A major advantage of the proposed structure is the possibility of obtaining avalanche gain in the silicon cladding. First experimental results have demonstrated the validity of the concept.     

Au掺杂HgCdTe材料的光电特性

Au掺杂是改善光伏型HgCdTe红外探测器性能的一种技术途径,通过Au掺杂来取代HgCdTe材料中的本征的Hg空位,可以提高材料的少子寿命和少子扩散长度。采用液相外延技术生长了Au掺杂的HgCdTe外延材料,Au的掺杂浓度为~8×1015/cm3,通过富Hg退火技术来抑制材料中的Hg空位,Hg空位的浓度控制在1~2×1015/cm3。变温霍尔测试表明,退火材料中的受主杂质能级为8~12 meV,并且与退火条件相关。采用Au掺杂材料和离子注入成结工艺制备了截止波长为14 μm的甚长波红外焦平面器件,测试结果显示,用Au掺杂取代Hg空位掺杂,可以显著提高红外探测器的光响应率,探测器的内量子效率可以达到95%以上。