共查询到20条相似文献，搜索用时 0 毫秒
1.
Zhaojun Liu 《中国物理 B》2022,31(12):128503-128503
We systematically investigate the influence of InSb interface (IF) engineering on the crystal quality and optical properties of strain-balanced InAs/GaSb type-II superlattices (T2SLs). The type-II superlattice structure is 120 periods InAs (8 ML)/GaSb (6 ML) with different thicknesses of InSb interface grown by molecular beam epitaxy (MBE). The high-resolution x-ray diffraction (XRD) curves display sharp satellite peaks, and the narrow full width at half maximum (FWHM) of the 0th is only 30-39 arcsec. From high-resolution cross-sectional transmission electron microscopy (HRTEM) characterization, the InSb heterointerfaces and the clear spatial separation between the InAs and GaSb layers can be more intuitively distinguished. As the InSb interface thickness increases, the compressive strain increases, and the surface \"bright spots\" appear to be more apparent from the atomic force microscopy (AFM) results. Also, photoluminescence (PL) measurements verify that, with the increase in the strain, the bandgap of the superlattice narrows. By optimizing the InSb interface, a high-quality crystal with a well-defined surface and interface is obtained with a PL wavelength of 4.78 μ, which can be used for mid-wave infrared (MWIR) detection. 相似文献
2.
3.
XUE Ting;HUANG Jianliang;YAN Shaolong;ZHANG Yanhua;MA Wenquan 《光子学报》2023,52(10):62-69
To reduce the cryogenic cooling cost for high operating temperature applications, the dark current of infrared photodetectors need to be further reduced. Many methods have been proposed such as inserting unipolar-barrier, complementary barriers, the M-structure, and double heterostructures. The Interband Cascade Infrared Photodetectors （ICIP）, originally arising from the interband cascade laser, has also been tried. The ICIP structure consists of high bandgap AlSb material, which can further reduce the dark current. Therefore, these features may make high temperature operation possible for ICIPs, especially for the mid wavelength range.This work investigates the ICIP for mid wavelength operation. The ICIP is designed as a p-i-n type. Specifically, the i region is composed of a 5-stage interband cascade structure. Each cascade stage consists of an electron-barrier （eB） layer, an absorber layer, and a hole-barrier （hB） layer, and this sequence repeats five times. The photogenerated electrons in one absorber layer should first pass through the hB layer by optical phonon assisted stepwise transport. The carriers, which arrive at the hole states of the eB layer, finally tunnel to the next absorber layer. Consequently, the energy levels of the eB and the hB layer should be equidistributed. In other words, the energy difference between adjacent levels should be comparable to the optical phonon energy, about 30 meV.The absorber layer of each period is designed as 0.5 μm thick InAs （2.4 nm）/GaSb （3.6 nm） SLs, which has an expected cut-off wavelength of around 4.28 μm. The hB layer is made up of 8 InAs QWs, separated by AlSb barrier layers. For the eB layer, it consists of AlSb（2.1 nm）/GaSb（5.3 nm）/AlSb（2.1 nm）/GaSb（7.5 nm）/AlSb（2.1 nm）. The calculated energy separation between adjacent levels is close to the optical phonon energy. The sample is grown on an n-type GaSb （001） substrate by molecular beam epitaxy. After the growth, an array mesa was formed using standard photolithography and dry-etched.We measured the temperature-dependent dark current to reveal the dark current mechanism of the device. The dark current of the device is dominated by the diffusion current instead of the generation-recombination current for the temperature range between 180 K and 300 K, as seen from the Arrhenius plot. The spectral responsivity is measured by calibrating the photocurrent spectrum with the blackbody response with the blackbody source temperature set at 800 K. We calculated the detectivity of the device. At 77 K, the 50% cutoff wavelength is 4.02 μm and the detectivity D * is 1.26×1012 cm·Hz1/2/W for the peak wavelength of 3.79 μm at 0 V. At 300 K, the 50% cutoff wavelength is 4.88 μm and the D * is 1.28×109 cm·Hz1/2/W for the peak response wavelength of 4.47 μm at 0 V.We also observed the Negative Difference Resistance （NDR） effect in our device. The NDR effect can be seen in the dark current curves from 77 K to 220 K. The I P （the NDR peak point current） has almost no change while the I V （the NDR valley point current） increases, and therefore the Peak-to-Valley Current Ratio （PVCR） （I P/I V） decreases with increasing temperature. There are two parts of the tunneling process arising from the interband cascade structures： tunneling through the electron barriers and resonant tunneling. As the dark current equation, ![]()
![]()
![]()
![]()
![]()
![]()
![]()
![]()
![]()
![]()
![]()
![]()
![]()
![]()
I V rises. Meanwhile, the ![]()
![]()
![]()
![]()
I P） is caused by the both two tunneling mechanism, leading to an almost constant peak dark current. Correspondingly, an unchanged I P and an increased I V lead to a smaller PVCR for a higher temperature. 相似文献
4.
In this paper, quantum efficiency (QE) measurements performed on type-II InAs/GaSb superlattice (T2SL) photodiodes operating in the mid-wavelength infrared domain, are reported. Several comparisons were made in order to determine the SL structure showing optimum radiometric performances: same InAs-rich SL structure with different active zone thicknesses (from 0.5 μm to 4 μm) and different active zone doping (n-type versus p-type), same 1 μm thick p-type active zone doping with different SL designs (InAs-rich versus GaSb-rich and symmetric SL structures). Best result was obtained for the p-type doped InAs-rich SL photodiode, with a 4 μm active zone thickness, showing a QE that reaches 61% at λ = 2 μm and 0 V bias voltage. 相似文献
5.
In this paper we report on the growth of mid-wavelength infrared superlattice materials by molecular beam epitaxy. We focused on the effects of process parameters, such as arsenic beam equivalent pressure and shutter sequences, on the key material properties, such as the lattice mismatch and the surface morphology. Though a smaller As beam equivalent pressure helps to reduce the lattice mismatch between the superlattice and the GaSb substrate, the As beam equivalent pressure itself has a lower limit below which the material’s surface morphology will degrade. To achieve fully lattice-matched superlattice materials, a novel shutter sequence in the growth process was designed. With well-designed interface structures, a high quality P-I-N superlattice mid-infrared detector structure was realized. At 77 K the dark current density at −50 mV bias was 2.4 × 10−8 A/cm2 and the resistance-area product (RA) at maximum (−50 mV bias) was 2.4 × 106 Ω cm2, and the peak detectivity was then calculated to be 9.0 × 1012 cm Hz1/2/W. The background limited infrared photodetector (BLIP) level can be achieved at a temperature of 113 K. 相似文献
6.
Fang-Qi Lin 《中国物理 B》2022,31(9):98504-098504
By optimizing the V/III beam-equivalent pressure ratio, a high-quality InAs/GaSb type-II superlattice material for the long-wavelength infrared (LWIR) range is achieved by molecular beam epitaxy (MBE). High-resolution x-ray diffraction (HRXRD), atomic force microscopy (AFM), and Fourier transform infrared (FTIR) spectrometer are used to characterize the material growth quality. The results show that the full width at half maximum (FWHM) of the superlattice zero-order diffraction peak, the mismatching of the superlattice zero-order diffraction peak between the substrate diffraction peaks, and the surface roughness get the best results when the beam-equivalent pressure (BEP) ratio reaches the optimal value, which are 28 arcsec, 13 arcsec, and 1.63 Å, respectively. The intensity of the zero-order diffraction peak is strongest at the optimal value. The relative spectral response of the LWIR detector shows that it exhibits a 100% cut-off wavelength of 12.6 μm at 77 K. High-quality epitaxial materials have laid a good foundation for preparing high-performance LWIR detector. 相似文献
7.
半导体纳米线作为纳米器件的作用区和连接部分具有理想的形状, 把电子运动和原子周期性限制在一维结构当中.通过体材料的已知特性, 有效地选择材料组分使纳米线的低维结构优点更加突出.此外, 还可以通过其他方式来调整纳米线特性, 如控制纳米线直径、晶体学生长方向、结构相、表面晶体学晶面和饱和 度等内部或固有的特性;施加电场、磁场、热场和力场等外部影响. 体材料InAs和GaSb的晶格常数非常相近, 因此InAs/GaSb异质结构晶格失配很小, 可生长成为优良的红外光电子材料.另外, 体材料InAs在二元III---V化合物半导体中具有最低的有效质量, 这使得电子限制在InAs层的InAs/GaSb超晶格具有良好的输运特性. 本文通过第一原理计算研究轴线沿[001]和[111]闪锌矿晶体学方向的 (InAs)1/(GaSb)1超晶格纳米线(下标表示分子或双原子单层的数量) 的结构、电子和力学特性, 以及它们随纳米线直径(线径约为0.5---2.0 nm)的变化规律.另外, 分析了外部施加的应力对电子特性的影响, 考察了不同线径(InAs)1/(GaSb)1超晶格纳米线的电子带边能级随轴向应变的变化, 从而确定超晶格电子能带的带边变形势. 相似文献
8.
利用第一原理平面波赝势法, 对(InAs)1/(GaSb)1超晶格原子链的原子结构、力学特性、电子能带结构、 声子结构和光学特性进行研究, 并结合密度泛函理论数值原子轨道赝势法和非平衡格林函数法计算量子输运特性. 与二维层结构的(InAs)1/(GaSb)1超晶格相比, (InAs)1/(GaSb)1超晶格原子链的能带结构有明显不同, 在某些情况下表现为金属能带特性. 对理想条件下(InAs)1/(GaSb)1 超晶格原子链的力学强度计算表明, 该结构可承受的应变高达 ε=0.19. 通过对声子结构的完整布里渊区分析, 研究了(InAs)1/(GaSb)1超晶格原子链的结构稳定性. 对两端接触电极为Al纳米线的InAs/GaSb超晶格原子链的电子输运特性计算表明, 电导随链长和应变的改变而发生非单调变化.光吸收谱的计算结果表现出在红外波段具有陡峭吸收边, 截止波长随超晶格原子链的结构而变化.预计InAs/GaSb超晶格原子链可应用于红外光电子纳米器件, 通过改变超晶格原子链的结构来调节光电响应波段. 相似文献
9.
Elena A. Plis Maya Narayanan Kutty Sanjay Krishna 《Laser u0026amp; Photonics Reviews》2013,7(1):45-59
InAs/(In,Ga)Sb Strained Layer Superlattices (SLSs) have made significant progress since they were first proposed as an infrared (IR) sensing material more than three decades ago. The basic material properties of SLS provide a prospective benefit in the realization of IR imagers with suppressed interband tunneling and Auger recombination processes, as well as high quantum efficiency and responsivity. With scaling of single pixel dimensions, the performance of focal plane arrays is strongly dependent on surface effects due to the large pixels’ surface/volume ratio. This article discusses the cause of surface leakage currents and various approaches of their reduction including dielectric passivation, passivation with organic materials (polyimide or various photoresists), passivation by overgrowth of wider bandgap material, and chalcogenide passivation. Performance of SLS detectors passivated by different techniques and operating in various regions of infrared spectrum has been compared. 相似文献
10.
F. Szmulowicz H. J. Haugan G. J. Brown K. Mahalingam B. Ullrich S.R. Munshi L. Grazulis 《Opto-Electronics Review》2006,14(1):69-75
The effect of interface anisotropy on the electronic structure of InAs/GaSb type-II superlattices is exploited in the design of thin-layer superlattices for mid-IR detection threshold. The design is based on a theoretical envelope function model that incorporates the change of anion and cation species across InAs/GaSb interfaces, in particular, across the preferred InSb interface. The model predicts that a given threshold can be reached for a range of superlattice periods with InAs and GaSb layers as thin as a few monolayers. Although the oscillator strengths are predicted to be larger for thinner period superlattices, the absorption coefficients are comparable because of the compensating effect of larger band widths. However, larger intervalence band separations for thinner-period samples should lead to longer minority electron Auger lifetimes and higher operating temperatures in p-type SLs. In addition, the hole masses for thinner-period samples are on the order the free-electron mass rather than being effectively infinite for the wider period samples. Therefore, holes should also contribute to photoresponse. A number of superlattices with periods ranging from 50.6 to 21.2 Å for the 4 μm detection threshold were grown by molecular beam epitaxy based on the model design. Low temperature photoluminescence and photoresponse spectra confirmed that the superlattice band gaps remained constant at 330 meV although the period changed by the factor of 2.5. Overall, the present study points to the importance of interfaces as a tool in the design and growth of thin superlattices for mid-IR detectors for room temperature operation. 相似文献
11.
We have demonstrated 384 × 288 pixels mid-wavelength infrared focal plane arrays (FPA) using type II InAs/GaSb superlattice (T2SL) photodetectors with pitch of 25 μm. Two p-i-n T2SL samples were grown by molecular beam epitaxy with both GaAs-like and InSb-like interface. The diode chips were realized by pixel isolation with both dry etching and wet etching method, and passivation with SiNx layer. The device one with 50% cutoff wavelength of 4.1 μm shows NETD ∼ 18 mK from 77 K to 100 K. The NETD of the other device with 50% cutoff wavelength at 5.6 μm is 10 mK at 77 K. Finally, the T2SL FPA shows high quality imaging capability at the temperature ranging from 80 K to 100 K which demonstrates the devices’ good temperature performance. 相似文献
12.
通过广义梯度近似的第一原理全电子相对论计算, 研究了不同界面类型InAs/GaSb超晶格的界面结构、电子和光吸收特性. 由于四原子界面的复杂性和低对称性, 通过对InAs/GaSb超晶格进行电子总能量和应力最小化来确定弛豫界面的结构参数. 计算了InSb, GaAs型界面和非特殊界面(二者交替)超晶格的能带结构和光吸收谱, 考察了超晶格界面层原子发生弛豫的影响.为了证实能带结构的计算结果, 用局域密度近似和Hartree-Fock泛函的平面波方法进行了计算. 对不同界面类型InAs/GaSb超晶格的能带结构计算结果进行了比较, 发现界面Sb原子的化学键和离子性对InAs/GaSb超晶格的界面结构、 能带结构和光学特性起着至关重要的作用. 相似文献
13.
We characterize the low-frequency white noise behavior of a large set of InAs/GaSb superlattice infrared pin-photodiodes for the mid-wavelength infrared regime at 3–5 μm. For diodes with an increased dark current in comparison to the dark current of generation–recombination limited bulk material, the standard shot-noise model fails to describe the noise experimentally observed in the white part of the spectrum. Instead, we find that McIntyre’s noise model for avalanche multiplication processes is compliant with our data. We suggest that within high electric field domains localized around macroscopic defects, avalanche multiplication processes leading to increased dark current and excess noise. 相似文献
14.
The efficacy of solution deposition of thiolated self-assembled monolayers (SAMs) has been explored for the purpose of passivating III–V type II superlattice (T2SL) photodetectors, more specifically a p-type heterojunction device. Sulfur passivation has previously been achieved on T2SL devices. However, degradation over time, temperature sensitivity and inconsistent reproducibility necessitate a physical encapsulate that can chemically bond to the chemical passivant. Thus, this research investigates two passivation methods, surface passivation with a thiol monolayer and passivation with a polymer encapsulant with a view toward future combination of these techniques. Analysis of the physical and chemical condition of the surface prior to deposition assisted in the development of ideal processes for optimized film quality. Successful deposition was facilitated by in situ oxide removal. Various commercially available functional (cysteamine) and non-functional (alkane) thiolated monolayers were investigated. Dark current was reduced by 3 orders of magnitude and achieved negligible surface leakage at low bias levels. The lowest dark current result, 7.69 × 10−6 A/cm2 at 50 mV, was achieved through passivation with cysteamine. 相似文献
15.
S. Kiravittaya H. Heidemeyer O. G. Schmidt 《Physica E: Low-dimensional Systems and Nanostructures》2004,23(3-4):253
The growth of a three-dimensional (3D) InAs quantum dot (QD) crystal on a patterned GaAs (0 0 1) substrate is demonstrated. The morphology of QDs grown on a surface patterned with shallow holes is studied as a function of the amount of deposited InAs. We observe that the QDs form in the patterned holes close to each other forming lateral QD bimolecules for InAs coverages below the commonly observed critical thickness of 1.6 monolayers. When the coverage increases, the QD bimolecules coalesce to form larger single QDs. The QDs in the holes are then capped with a Ga(Al)As spacer. The buried QD array serves as a strain template for controlling the formation site of the QDs in the second layer. By tuning the growth conditions for the second and subsequent layers, we achieve a 3D InAs QD crystal with a high degree of perfection. A detail investigation of the growth on hole patterns with different periodicities is presented. 相似文献
16.
17.
In this paper, we present a range of modeling tools that are used in the design and performance evaluation of type-II superlattice detectors. Among these is an optical and photo carrier transport model for the spectral total external QE, which takes into account carrier diffusion length. Using this model, the diffusion length is extracted from external quantum efficiency measurements. It can also be used to fine-tune an optical cavity in relation to the wavelength range of interest for optimal quantum efficiency. Furthermore, an electrical device model for band bending, dark current and doping optimization is described. The modeling tools are discussed and examples of their use are given for MWIR type-II detectors based on InAs/AlSb/GaSb superlattices. 相似文献
18.
We have implemented first-principles relativistic pseudopotential calculations within general gradient approximation to investigate the structural and electronic properties of quaternary InAs/GaSb superlattices with an InSb or GaAs type of interface. Because of the complexity and low symmetry of the quaternary interfaces, the interface energy and strain in the InAs/GaSb superlattice system have been calculated to determine the equilibrium interface structural parameters. The band structures of InAs/GaSb superlattices with InSb and GaAs interfaces have been calculated with respect to the lattice constant and atomic position relaxations of the superlattice interfaces. The calculation of the relativistic Hartree–Fock pseudopotential in local density approximation has also been performed to verify the calculated band structure results that have been predicted in other empirical theories. The calculated band structures of InAs/GaSb superlattices with different types of interface (InSb or GaAs) have been systematically compared. We find that the virtual–crystal approximation fails to properly describe the quaternary InAs/GaSb superlattice system, and the chemical bonding and ionicity of anion atoms are essential in determining the interface and electronic structures of InAs/GaSb superlattice system. 相似文献
19.
Makoto Kudo Tomoyoshi Mishima Satoshi Iwamoto Toshihiro Nakaoka Yasuhiko Arakawa 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):275
Self-assembled GaSb quantum dots (QDs) with a photoluminescence wavelength longer than 1.3 μm were successfully grown by suppressing the replacement of As and Sb on the surface of the GaSb QDs. This result means that GaSb can thus join InAs or GaInAs as a suitable material for QD lasers for optical communications. 相似文献
20.
Current–voltage characteristics of long-wave infrared (LWIR) InAs/GaSb strained layer superlattice photodiodes (cut-off wavelength ∼10 μm), passivated with different surface passivants, have been modeled and simulated using ATLAS software from SILVACO. The simulated results are fitted to previous experimental results obtained on unpassivated devices and those passivated by silicon-dioxide (SiO2), silicon nitride (SixNy) and zinc sulfide (ZnS). Surface parameters in terms of surface recombination velocity, shunt resistance and interface trap density are extracted for different passivants. The performance of silicon-dioxide passivated diode is solely dominated by a shunt leakage path with a shunt resistance value of 0.56 Ω-cm2. Extracted electron and hole surface recombination velocities have values of 105 cm/s and 107 cm/s for unpassivated, 103 cm/s and 105 cm/s for SixNy passivated and 102 cm/s and 103 cm/s for ZnS passivated devices. Interface trap density follows a similar trend with values of 1015 cm−2, 8.5 × 1014 cm−2 and 1010 cm−2 for unpassivated, SixNy passivated and ZnS passivated devices respectively. The suitability and limitations of the simulation tool are discussed. 相似文献