Structural design of mid-infrared waveguide detectors based on InAs/GaAsSb superlattice

In the realm of near-infrared spectroscopy,the detection of molecules has been achieved using on-chip waveguides and resonators.In the mid-infrared band,the integration and sensitivity of chemical sensing chips are often constrained by the reliance on off-chip light sources and detectors.In this study,we demonstrate an InAs/GaAsSb superlattice mid-infrared waveguide integrated detector.The GaAsSb waveguide layer and the InAs/GaAsSb superlattice absorbing layer are connected through evanescent coupling,facilitating efficient and highquality detection of mid-infrared light with minimal loss.We conducted a simulation to analyze the photoelectric characteristics of the device.Additionally,we investigated the factors that affect the integration of the InAs/GaAs⁃Sb superlattice photodetector and the GaAsSb waveguide.Optimal thicknesses and lengths for the absorption lay⁃er are determined.When the absorption layer has a thickness of 0.3μm and a length of 50μm,the noise equiva⁃lent power reaches its minimum value,and the quantum efficiency can achieve a value of 68.9%.The utilization of waveguide detectors constructed with Ⅲ-Ⅴ materials offers a more convenient means of integrating mid-infra⁃red light sources and achieving photoelectric detection chips.

Low Crosstalk Three-Color Infrared Detector by Controlling the Minority Carriers Type of InAs/GaSb Superlattices for Middle-Long and Very-Long Wavelength

We report a type-Ⅱ InAs/GaSb superlattice three-color infrared detector for mid-wave （MW）, long-wave （LW）, and very long-wave （VLW） detections. The detector structure consists of three contacts of NIPIN architecture for MW and LW detections, and hetero-junction NIP architecture for VLW detection. It is found that the spectral crosstalks can be significantly reduced by controlling the minority carriers transport via doping beryllium in the two active regions of NIPIN section. The crosstalk detection at MW, LW, and VLW signals are achieved by selecting the bias voltages on the device. At 77K, the cutoff wavelengths of the three-color detection are 5.3μm （at OmV）, 141μm （at 300mV） and 19μm （at -20mV） with the detectivities of 4.6xlO11 cm.Hzl/ZW-1, 2.3×10^10 cm.Hzl/2W-1, and 1.0×10^10cm.Hzl/2W-1 for MW, LW and VLW. The crosstalks of the MW channel, LW channel, and VLW channel are almost 0, 0.25, and 0.6, respectively.

Interface effect on superlattice quality and optical properties of InAs/GaSb type-Ⅱ superlattices grown by molecular beam epitaxy

We systematically investigate the influence of InSb interface(IF)engineering on the crystal quality and optical properties of strain-balanced InAs/GaSb type-Ⅱsuperlattices(T2SLs).The type-Ⅱsuperlattice structure is 120 periods InAs(8 ML)/GaSb(6 ML)with different thicknesses of InSb interface grown by molecular beam epitaxy(MBE).The highresolution 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 4.78μm,which can be used for mid-wave infrared(MWIR)detection.

1280×1024元InAs/GaSb II类超晶格中/中波双色红外焦平面探测器

本文报道了1280×1024元InAs/GaSb II类超晶格中/中波双色红外焦平面阵列探测器的研究结果。探测器采用PN-NP叠层双色外延结构,信号提取采用叠层双色结构和顺序读出方式。运用分子束外延技术在GaSb衬底上生长超晶格材料,双波段红外吸收区的超晶格周期结构分别为中波1:6 ML InAs/7 ML GaSb和中波2:9 ML InAs/7 ML GaSb。焦平面阵列像元中心距为12μm。在80 K时测试,器件双波段的工作谱段为中波1:3~4μm,中波2:3.8~5.2μm。中波1器件平均峰值探测率达到6.32×10^(11) cm·Hz^(1/2)W^(-1),中波2器件平均峰值探测率达到2.84×10^(11) cm·Hz^(1/2)W^(-1)。红外焦平面偏压调节成像测试得到清晰的双波段成像。本文是国内首次报道1280×1024规模InAs/GaSb II类超晶格中/中波双色红外焦平面探测器。

基于AlAsSb/InAsSb超晶格势垒的InAs/InAsSbⅡ类超晶格nBn中波红外探测器

InAs/InAsSbⅡ类超晶格避免了InAs/GaSbⅡ类超晶格中与Ga原子相关的缺陷复合中心,具有更高的少数载流子寿命,在高工作温度中波红外探测器制备方面有着良好的应用前景。少数载流子单极势垒结构通常被用来抑制探测器暗电流,如nBn结构探测器。在InAs/InAsSbⅡ类超晶格nBn中波红外光电探测器中,势垒层常采用AlAsSb等多元合金材料,阻挡多数载流子的输运。然而,势垒层与吸收层存在的价带偏移(VBO)使得光电流往往需要在大偏压下饱和,从而增大了探测器暗电流。本文设计了一种AlAsSb/InAsSb超晶格势垒,旨在消除VBO并降低量子效率对偏压的依赖性。研究结果显示,150 K下,设计制备的nBn光电探测器的50%截止波长为4.5μm,探测器光响应在-50 mV的小反向偏压下达到了饱和,3.82μm处的峰值响应度为1.82 A/W,对应量子效率为58.8%。在150 K和-50 mV偏压下,探测器的暗电流密度为2.01×10^(-5)A/cm^(2),计算得到在3.82μm的峰值探测率为6.47×10^(11)cm·Hz^(1/2)/W。

InAs/GaSb超晶格台面刻蚀工艺研究综述

本文综述了InAs/GaSb超晶格台面刻蚀工艺研究。从湿法和干法刻蚀的物理化学机理以及参数调控等方面进行分析,旨在阐明工艺条件对台面形貌的影响,以抑制带隙较窄的长波和甚长波超晶格表面漏电流。结果表明,湿法刻蚀中恰当的腐蚀液配比可以实现两种组分的均匀性刻蚀,而不会导致粗糙的表面和严重的下切;干法刻蚀中,采用Cl_(2)基和CH 4基混合气体,通过调整刻蚀气体类型及比例可实现物理和化学刻蚀两个过程的平衡,保证台面侧壁平滑性和倾角的垂直度。另外,对于不同组分的超晶格,需要选择不同的工艺参数才能满足InAs和GaSb的协同性刻蚀。最后对InAs/GaSb超晶格台面刻蚀工艺作出了展望。

Etching mask optimization of InAs/GaSb superlattice mid-wavelength infared 640×512 focal plane array

In this paper we focused on the mask technology of inductively coupled plasma（ICP） etching for the mesa fabrication of infrared focal plane arrays（FPA）.By using the SiO_2 mask,the mesa has higher graphics transfer accuracy and creates less micro-ripples in sidewalls.Comparing the IV characterization of detectors by using two different masks,the detector using the SiO_2 hard mask has the R_0A of 9.7×10~6 Ω·cm^2,while the detector using the photoresist mask has the R_0A of3.2 × 10~2 Ω·cm^2 in 77 K.After that we focused on the method of removing the remaining SiO_2 after mesa etching.The dry ICP etching and chemical buffer oxide etcher（BOE） based on HF and NH4 F are used in this part.Detectors using BOE only have closer R_0A to that using the combining method,but it leads to gaps on mesas because of the corrosion on AlSb layer by BOE.We finally choose the combining method and fabricated the 640×512 FPA.The FPA with cutoff wavelength of 4.8 μm has the average R_0A of 6.13 × 10~9 Ω·cm^2 and the average detectivity of 4.51 × 10~9 cm·Hz^（1/2）.W^（-1）at 77 K.The FPA has good uniformity with the bad dots rate of 1.21%and the noise equivalent temperature difference（NEDT） of 22.9 mK operating at 77 K.

Molecular Beam Epitaxy of Zero Lattice-Mismatch InAs/GaSb Type-Ⅱ Superlattice

Type-Ⅱ InAs/GaSb superlattiees made of 13 InAs monolayers （MLs） and 7 GaSb MLs are grown on GaSb substrates by solid source molecular beam epitaxy. To obtain lattice-matched structures, thin InSb layers are inserted between InAs and GaSb layers. We complete a series of experiments to investigate the influence of the InSb deposition time, Ⅴ/Ⅲ beam-equivalent pressure ratio and interruption time between each layer, and then characterize the superlattice （SL） structures with high-resolution x-ray diffraction and atomic force microscopy. The optimized growth parameters are applied to grow the 100-period SL structure, resulting in the full-width half-maximum of 29.55 arcsee for the first SL satellite peak and zero lattice-mismatch between the zero-order SL peak and the GaSb substrate peak.

Effect of compensation doping on the electrical and optical properties of mid-infrared type-II InAs/GaSb superlattice photodetectors

This paper presents a theoretical study on the electrical and optical properties of mid-infrared type-II InAs/GaSb superlattices with different beryllium concentrations in the InAs layer of the active region. Dark current, resistancearea product, absorption coefficient and quantum efficiency characteristics are thoroughly examined. The superlattice is residually n-type and it becomes slightly p-type by varying beryllium-doping concentrations, which improves its electrical performances. The optical performances remain almost unaffected with relatively low p-doping levels and begin to deteriorate with increasing p-doping density. To make a compromise between the electrical and optical performances, the photodetector with a doping concentration of 3 ×10^15 cm-3 in the active region is believed to have the best overall performances.

原子层沉积Al_(2)O_(3)钝化对InAs/InGaAsSbⅡ类超晶格发光特性的影响

提出一种基于干法刻蚀与原子层沉积相结合的钝化方法,采用干法刻蚀去除InAs/InGaAsSb超晶格表面及端面固有的氧化层,利用原子层沉积Al_(2)O_(3)薄膜钝化刻蚀表面,对钝化前后光致发光光谱的表征研究其发光性能与长期稳定性。处理后超晶格的As 3d谱中As-O键相关的峰消失表明其表面的氧化物被有效去除。样品的发光强度与激发光功率之间的拟合系数α从1.17减小为1.02,表明激子主导的发光占比增加。连续五天的红外光谱测试发现,处理后样品发光强度降低为原来的89%,而未处理样品的发光强度降低为原来的76%,表明处理后超晶格表现出更好发光稳定性。本研究为提升InAs/InGaAsSb超晶格性能、促进其光电探测领域的应用提供参考。

High-operating-temperature MWIR photodetector based on a InAs/GaSb superlattice grown by MOCVD

We demonstrate a high-operating-temperature(HOT)mid-wavelength InAs/GaSb superlattice heterojunction in-frared photodetector grown by metal-organic chemical vapor deposition.High crystalline quality and the near-zero lattice mis-match of a InAs/GaSb superlattice on an InAs substrate were evidenced by high-resolution X-ray diffraction.At a bias voltage of-0.1 V and an operating temperature of 200 K,the device exhibited a 50%cutoff wavelength of~4.9μm,a dark current dens-ity of 0.012 A/cm^(2),and a peak specific detectivity of 2.3×10^(9) cm·Hz^(1/2)/W.

Short-wavelength infrared InAs/GaSb superlattice hole avalanche photodiode

We demonstrate two short-wavelength infrared avalanche photodiodes based on InAs/GaSb superlattice grown by metal-organic chemical vapor deposition.The difference between the two devices,namely,p+n-n+and p+nn-n+,is that the p+nn-n+device possesses an additional middle-doped layer to separate the multiplication region from the absorption region.By properly controlling the electric field distribution in the p+nn-n+device,an electric field of 906 kV/cm has been achieved,which is 2.6 times higher than that in the p+n-n+device.At a reverse bias of-0.1 V at 77 K,both devices show a 100%cut-off wavelength of 2.25μm.The p+n-n+and p+nn-n+show a dark current density of 1.5×10^-7 A/cm^2 and 1.8×10^-8 A/cm^2,and a peak responsivity about 0.35 A/W and 0.40 A/W at 1.5μm,respectively.A maximum multiplication gain of 55 is achieved in the p+nn-n+device while the value is only less than 2 in the p+n-n+device.Exponential nature of the gain characteristic as a function of reverse bias confirms a single carrier hole dominated impact ionization.

Growth of high material quality InAs/GaSb type-Ⅱ superlattice for long-wavelength infrared range by molecular beam epitaxy

By optimizing theⅤ/Ⅲbeam-equivalent pressure ratio,a high-quality InAs/GaSb type-Ⅱsuperlattice 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?,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 12.6μm at 77 K.High-quality epitaxial materials have laid a good foundation for preparing high-performance LWIR detector.

长波InAs/GaSbⅡ类超晶格红外探测器

报道了50%截止波长为12.5μm的InAs/GaSb Ⅱ类超晶格长波红外探测器材料及单元器件.实验采用分子束外延技术在GaSb衬底上生长超晶格材料.吸收区结构为15ML(InAs)/7ML(GaSb),器件采用PBIN的多层异质结构以抑制长波器件暗电流.在77K温度下测试了单元器件的电流-电压(Ⅰ-Ⅴ)特性,响应光谱和黑体响应.在该温度下,光敏元大小为100μm×100μm的单元探测器RmaxA为2.5Ωcm2,器件的电流响应率为1.29A/W,黑体响应率为2.1×109cmHz1/2/W,11μm处量子效率为14.3%.采用四种暗电流机制对器件反向偏压下的暗电流密度曲线进行了拟合分析,结果表明起主导作用的暗电流机制为产生复合电流.

InAs/GaSb超晶格中波焦平面材料的分子束外延技术

报道了InAs/GaSb超晶格中波材料的分子束外延生长技术研究.通过改变GaSb衬底上分子束外延InAs/GaSb超晶格材料的衬底温度,以及界面的优化等,改善超晶格材料的表面形貌和晶格失配,获得了晶格失配Δa/a=1.5×10-4,原子级平整表面的InAs/GaSb超晶格材料,材料77 K截止波长为4.87μm.

GaAs基GaSb体材料及InAs/GaSb超晶格材料的MBE生长

采用分子束外延方法在GaAs（100）衬底上生长GaSb体材料,以此GaSb为缓冲层生长了不同InAs厚度的InAs/GaSb超晶格,其10K光致发光谱峰值波长在2.0~2.6μm.高分辨透射电子显微镜观察证实超晶格界面清晰,周期完整.

InAs/GaSb超晶格红外探测器台面湿法腐蚀研究

研究了不同腐蚀体系对InAs/GaSb超晶格材料台面的刻蚀,并从中选择了由氢氟酸、酒石酸和双氧水构成的酒石酸腐蚀体系。该体系较适合InAs/GaSb超晶格材料的刻蚀,刻蚀速率稳定,下切效应小。进一步研究发现当HF达到一定浓度后不再影响刻蚀速度;在较低的酒石酸和双氧水浓度下,刻蚀速度是由氧化过程控制,且反应速度和双氧水的浓度成正比。腐蚀液配比为酒石酸(3.5g)∶H2O2(4mL)∶HF(1mL)∶H2O(400mL),刻蚀速度约为0.5μm/min。

320×256元InAs/GaSb II类超晶格中波红外双色焦平面探测器

报道了320×256元InAs/GaSb II类超晶格红外双色焦平面阵列探测器的初步结果.探测器采用PN-NP叠层双色外延结构,信号提取采用顺序读出方式.运用分子束外延技术在GaSb衬底上生长超晶格材料,双波段红外吸收区的超晶格周期结构分别为7 ML InAs/7 ML GaSb和10 ML InAs/10 ML GaSb.焦平面阵列像元中心距为30μm.在77 K时测试,器件双色波段的50%响应截止波长分别为4.2μm和5.5μm,其中N-on-P器件平均峰值探测率达到6.0×10^(10) cmHz^(1/2)W^(-1),盲元率为8.6%;P-on-N器件平均峰值探测率达到2.3×10~9 cmHz^(1/2)W^(-1),盲元率为9.8%.红外焦平面偏压调节成像测试得到较为清晰的双波段成像.

InAs／GaSbⅡ型超晶格的拉曼和光致发光光谱

采用分子束外延(MBE)技术,在GaSb(100)衬底上外延生长晶体结构完整和表面平整的Ⅱ型超晶格InAs(1.2nm)/GaSb(2.4nm)。拉曼光谱表明:随着温度从70K升高至室温,由于热膨胀作用和光声子散射过程中的衰减,超晶格纵光学声子拉曼频移向低波数方向移动5cm-1,频移温度系数约为0.023cm-1/K。光致发光(PL)峰在2.4～2.8μm,由带间辐射复合和束缚激子复合构成,2.55μmPL峰随温度变化(15～150K)发生微小红移,超晶格中InAs电子带与GaSb空穴带带间距随温度变化比体材料的禁带宽度小。PL发光强度在15～50K随温度升高而升高,在60～150K则相反,并在不同温度段表现出不同的温度依赖关系。

InAs/GaSbⅡ类超晶格中波红外探测器

InAs/GaSb II类超晶格探测器是近年来国际上发展迅速的红外探测器,其优越性表现在高量子效率和高工作温度,以及良好的均匀性和较低的暗电流密度,因而受到广泛关注。报道了InAs/GaSb超晶格中波材料的分子束外延生长和器件性能。通过优化分子束外延生长工艺,包括生长温度和快门顺序等,获得了具原子级表面平整的中波InAs/GaSb超晶格材料,X射线衍射零级峰的双晶半峰宽为28.8″,晶格失配Δa/a=1.5×10-4。研制的p-i-n单元探测器在77 K温度下电流响应率达到0.48 A/W,黑体探测率为4.54×1010cmHz1/2W,峰值探测率达到1.75×1011cmHz1/2W。