非均匀GaAs/AlGaAs量子阱红外探测器材料表征和器件性能研究

本文利用分子束外延（MBE）技术成功生长了GaAs/AlGaAs非均匀量子阱红外探测器材料,并对相关微结构作了细致表征。分析比较了非均匀量子阱结构和常规量子阱红外探测器性能差异,并对比研究了不同势阱宽度下非均匀量子阱红外探测器的性能变化。通过高分辨透射电子显微镜（HRTEM）结合能谱仪（EDS）对非均匀量子阱红外探测器材料微结构进行了分析,并利用二次离子质谱仪（SIMS）对非均匀势阱掺杂进行了表征。结果表明,该量子阱外延材料晶体质量很好,量子阱结构和掺杂浓度也与设计值符合较好。对于非均匀量子阱红外探测器,通过改变每个阱的掺杂浓度和势垒宽度,可以改变量子阱电场分布,而与传统的均匀量子阱红外探测器相比,其暗电流显著下降（约一个数量级）。在不同阱宽下,非均匀量子阱的跃迁模式发生改变,束缚态到准束缚态跃迁模式下（B-QB）的器件具有较高的黑体响应率以及较低的暗电流。     

中/长波切换工作模式的双色量子阱红外焦平面研制

报道了中/长波切换工作模式的双色量子阱红外焦平面研制。通过特殊设计的器件和读出电路结构,获得了可对中波波段和长波波段选择的切换架构。突破了双色量子阱材料、器件以及读出电路等关键技术,研制出384288规模、25 m中心距双色量子阱红外焦平面探测器。在70 K条件下器件性能优良,噪声等效温差为28 mK(中波)和30 mK(长波),响应峰值波长分别为5.1 m(中波)和8.5 m(长波)。室温目标红外成像演示了探测器的双色探测功能。     

等离激元微腔耦合长波红外量子阱高消光比偏振探测器（特邀）

长波红外偏振探测器能够大幅提升对热成像目标的识别能力。受制于衍射极限的物理限制,目前的微线栅偏振片型长波红外偏振探测器的偏振消光比基本上只能做到最高10∶1左右。文中采用金属/介质/金属的等离激元微腔结构,将量子阱红外探测激活层相嵌在微腔之中。由于上、下金属之间的近场耦合形成了在双层金属区域的横向法布里-珀罗共振模式,构成等离激元微腔。文中利用微腔的模式选择特性及其与量子阱子带间跃迁的共振耦合,将量子阱子带跃迁不能直接吸收的垂直入射光耦合进入等离激元微腔并转变为横向传播,从而能够被量子阱子带吸收,实现了在长波红外13.5 μm探测波长附近偏振消光比大于100∶1的结果。相关工作为发展我国高消光比长波红外偏振成像焦平面提供了全新的物理基础和技术路径。     

量子阱红外探测器

评述了半导体量子阱内子带间光跃迁的主要特性以及量子阱红外探测器的物理问题和器件结构特点,介绍了国外在此领域研究的最新进展,讨论了有关子带间跃迁和量子阱红外探测器研究的若干发展趋势.     

中波-长波红外双色QWIP探测器设计

双色QWIP是一类重要的第三代红外探测器,但很少有研究报道对其有源区结构以及耦合光栅参数进行系统的计算分析和优化设计。文中基于包络函数近似、传输矩阵模型、经典光学原理等理论对中波-长波红外双色QWIP探测器的多周期有源区以及二维耦合光栅进行了较为详细的优化设计。长波红外(LWIR)有源区采用GaAs/AlGaAs准匹配体系的多量子阱结构,峰值响应波长为8.5 m;中波红外(MWIR)有源区采用InGaAs/GaAs/AlGaAs应变体系的微带超晶格结构,峰值响应波长为4.5 m;子带间跃迁类型均设计为束缚态-准束缚态(B-QB)以降低暗电流,提高探测率。此外,通过折衷优化设计,采用单周期二维光栅以有效实现LWIR与MWIR的双色耦合。上述设计对双色QWIP器件的研制具有较好的实际指导意义。     

GaAs／AlGaAs量子阱红外探测器的光荧光表征

对GaAs/AlGaAs量子阱红外探测器器件进行显微荧光光谱（μ－PL）测量,光谱中表征势垒、势阱基态间光跃迁能量位置的荧光峰值接与势垒中Al含量相关,通过光谱实验上对势垒和量子阱带间跃迁能量的确定并结合有效质量理论的计算,获得了Al组分和阱宽值,并由此推算出相应的红外探测响应波长,与光电流谱的结果相比吻合良好,这种材料的测量结果有利于器件制备的材料筛选。     

GaAs/GaAlAs量子阱双色红外探测器的光电性质的研究

本文综述了有关新型的GaAs／AlGaAs体系双色量子阱红外探测器的结构特性和光电特性的研究工作．双色探测器工作在3～5μm及8～12μm大气窗口波段范围，是光伏响应模式和光导响应模式相结合的偏压控制型两端器件．研究内容包括探测器的器件结构特性、红外光吸收特性、红外光电流响应、暗电流、噪声特性和探测率测试分析等等．首次从理论和实验两方面探讨有关量子阱束缚子能带到扩展态中不同虚能组之间的光跃迁问题及光电子输运问题．     

GaAs/Al_xGa_(1-x)As量子阱红外探测器光谱特性的研究

采用MBE法制备了不同结构参数及不同阱中掺杂浓度的GaAs/AlxGa1-xAs量子阱红外探测器外延材料。通过对量子阱红外探测器材料特性和器件特性的实验测试及理论分析,研究了量子阱红外探测器的响应光谱特性,并通过薛定谔方程和泊松方程的求解,对掺杂对量子阱能级的影响做了研究。结果表明,由于应力导致的能带非抛物线性使得阱中能级发生了变化,从而引起吸收峰向高能方向发生了漂移,而阱中进行适度的掺杂没有对量子阱能级造成影响,光致发光谱实验结果与之吻合较好。在光电流谱的实验分析基础之上,分析了量子阱阱宽、Al组分与峰值探测波长λ的关系,为量子阱红外探测器的设计优化提供了参考。     

局域光场增强的量子阱红外探测器（特邀）

量子阱红外探测器是继碲镉汞红外探测器之后又一重要的可以在中、长波段和甚长波段工作的红外探测器件。它在长波红外探测、多色探测及其焦平面技术方面表现出比碲镉汞红外探测器更具特色的优势,对量子阱红外探测器的研究将在很大程度上推动我国红外探测器技术的发展。这一探测器的突出优势是其材料均匀性好,制备技术成熟。但是由于量子效率偏低,且无法直接吸收垂直入射红外光,所以需要针对不同的红外探测波段,设计和制备各类光栅或微腔结构来进行光耦合及局域光场增强以有效提升探测器性能。如何更有效提升量子阱红外探测器的光耦合效率,降低暗电流,提高器件工作温度是仍然是目前研究的重点。文中着重介绍和总结了近5年来研究的局域光场增强的新型量子阱红外探测器,从提高探测器光耦合效率、降低器件暗电流和提高工作温度等方面重点讨论各种量子阱红外探测器的新结构和新机理,同时展望了这一探测器的未来发展方向。     

128×128三电极中/长波双色量子阱红外探测器

量子阱红外探测器(QWIP)阵列具有重要的实用意义。国外的研究已经相当成熟,但是在国内,量子阱红外探测器阵列的研究水平还较低,尤其是对于双色量子阱红外探测器阵列的研究更是刚刚起步。文中使用GaAs/AlGaAs、InGaAs/AlGaAs应变量子阱和三端电极引出的器件结构研制出128×128中/长波双色量子阱红外探测器阵列。该结构实现了同像元同时引出双色信号。器件像元中心距为40μm,像元有效面积为36μm×36μm。探测器芯片与读出电路互连并完成微杜瓦封装。在65 K条件下测试,峰值波长为:中波5.37μm,长波8.63μm,器件的平均峰值探测率为:中波4.75×109cmHz1/2W-1,长波3.27×109cmHz1/2W-1。并进行了双波段的红外演示成像。     

QUANTUM MECHANICAL MODEL AND SIMULATION OF GaAs／AlGaAs QUANTUM WELL INFRARED PHOTODETECTOR—Ⅱ ELECTRICAL ASPECTS

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QUANTUM MECHANICAL MODEL AND SIMULATION OF GaAs/AlGaAs QUANTUM WELL INFRARED PHOTO- DETECTOR-Ⅰ OPTICAL ASPECTS

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｆｒａｒｅｄｄｅｔｅｃｔｏｒｔｅｃｈｎｉｑｕｅｈａｓｂｅｅｎａｋｅｙｆａｃｔｏｒｉｎｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｔｈｅｉｎｆｒａｒｅｄｔｅｃｈｎｏｌｏｇｙｆｏｒｍｏｒｅｔｈａｎ 4 0 ｙｅａｒｓ .Ｓｉｎｃｅ 1970 ,ｓｅｍｉｃｏｎｄｕｃｔｏｒｓｌｉｋｅＩｎＳｂａｎｄＨｇＣｄＴｅｈａｖｅｂｅｅｎｔｈｅｐｒｉｎｃｉｐａｌｍａｔｅｒｉａｌｓｆｏｒｖａｒｉｏｕｓｉｎｆｒａｒｅｄｄｅｔｅｃｔｏｒａｐｐｌｉｃａｔｉｏｎｓ .Ｔｈｅｆｏｒｍａｔｏｆｔｈｅｉｎｆｒａｒｅｄｄｅｔｅｃｔｏｒｍｏｔｉｖａｔｅｄｂｙｓｍａｒｔｔｈｅｒｍａｌｉｍａｇｉｎｇｓｙｓｔｅｍｃｈａｎｇｅｄｆｒｏｍｓｉｎｇｌｅｅｌｅｍｅｎｔｄｅｖｉｃｅｔｏｆｏｃａｌｐｌａｎａｒｒａｙｓ(ＦＰＡｓ)ｉｎｔｈｅｍｉｄｄｌｅｏｆ 80’ｓ [1].Ｔｏｄａｙ’ｓｔｅｃｈｎｏｌｏｇｙｏｆｉｎｆｒａｒｅｄｄｅｔｅｃｔｏｒｃｏｎｃｅｎｔｒａｔｅｓｌａｒｇｅｌｙｏｎｆｏｃａｌｐｌａｎａｒｒａｙｓ ,ｅｘｐｅｃｉａｌｌｙｆｏｒｓｅｎｓｉｔｉｖｅ ,ｈｏｍｏｇｅｎｅｏｕｓａｎｄｌａｒｇｅｆｏｒｍａｔｓｃａｌｅｄｅｖｉｃｅｓ .ＨｇＣｄＴｅ...     

GaAs／AlGaAs多量子阱红外探测器的光电流谱

测量了ＧａＡｓ／ＡｌＧａＡｓ多量子阱红外探测器在零偏压、小偏流和大偏压等条件下的光电流谱，并结合理论计算的光跃迁能量讨论了光电流谱的多峰结构和异常增强特性。     

Strain effect on intersubband transitions in rolled-up quantum well infraredphotodetectors

Pre-strained nanomembranes with four embedded quantum wells (QWs) are rolled up into threedimensional (3D) tubular QW infrared photodetectors (QWIPs),which are based on the QW intersubband transition (ISBT).A redshift of~0.42 meV in photocurrent response spectra is observed and attributed to two strain contributions due to the rolling of the pre-strained nanomembranes.One is the overall strain that mainly leads to a redshift of~0.5 meV,and the other is the strain gradient which results in a very tiny variation.The blue shift of the photocurrent response spectra with the external bias are also observed as quantum-confined Stark effect (QCSE) in the ISBT.     

Transient response times of a-Si : H p-i-n color detector

Transients and relevant response times of a-Si : H p-i-n photodetector under various illuminations (in the visible range) and bias voltage conditions were studied. The model/method for possible color detection using on and off transient response times is proposed. Depending on illumination and bias pulse types, one or two processes are found to be involved in the conduction mechanism, including transition and trapping of both charge carrier types. Characteristic photocurrent transients and response times under modulated monochromatic and chromatic visible light illumination enable color recognition. The peculiar behavior of the blue light transients has been also plausibly explained by means of the proposed model.     

A high-speed intersubband modulator based on quantum interferencein double quantum wells

Calculations on a modulator based on quantum interference in AlGaAs/GaAs asymmetric double quantum wells (QWs) are performed. The modulation of the absorption is based on the anti-crossing behavior of the two lowest states in the coupled wells. At anti-crossing, the oscillator strengths of the transitions from these two lowest states to a higher state are changed in opposite directions. The width of the barrier between the wells should be thick enough to allow a large change in oscillator strength with applied field, yet thin enough so that the absorption peaks of the transitions are resolved. The QWs are designed so that one absorption peak has only a small energy shift for the transition used for modulation while the absorption varies rapidly with the applied voltage. A complete structure including a surface plasmon waveguide is proposed enabling calculations of modal absorption. Parameters important for the performance of the modulator are then determined. An extinction ratio of 10 dB at a wavelength of 8.4 μm is predicted for a device length of 18 μm and a peak-to-peak voltage of 0.9 V. The resistance-capacitance-limited 3-dB bandwidth is 130 GHz. The predicted performance compares very favorably with present interband modulators based on the quantum-confined Stark effect     

Characterizing electric fields in (111)B InGaAs quantum wells using electric field modulated photoluminescence and reflectance techniques

We have performed a series of electroreflectance, photoluminescence, and electric-field-modulated photoluminescence experiments to characterize the strain-induced electric fields in (111)B InGaAs/AlGaAs quantum well p-i-n diode structures. A 180° phase change in the lineshapes of electroreflectance spectra of these samples determines when the quantum well is biased to flatband. Using this bias and a depletion model for the diode, the polarization field in the quantum well can be determined. Contrary to expectations, this polarization field increases significantly with increasing temperature. In addition, at fixed temperature, the quantum well transition energies red-shift with increasing excitation intensity when excited by photons of energy higher than the lowest quantum well transition but lower than the AlGaAs diode's bandgap. When excited with photons of energy greater than the AlGaAs bandgap, the transition energy first red shifts then blue shifts with increasing excitation intensity.     

多量子阱的电子干涉及引起的光电流特性

根据电子干涉理论分析指出：多量子阱结构势垒以上的电子,由于其干涉效应形成一些分立的弱干涉非定域态。当存在光激发时,量子阱中基态电子可跃迁到这些弱干涉非定域态上,在外电场作用下形成光电流谱的峰结构。理论计算出的几个光电流峰位置与实验测量的结果符合较好。     

用PL谱评测多量子阱红外探测器外延材料

对GaAs/AlGaAs多量子阱红外探测器外延材料进行了光致荧光谱(PL)测量,结合理论计算,由材料吸收峰位置得到势垒高度以及势阱基态位置,并由此推算出相应的红外探测响应波长。推算结果与器件光电流实验值的对比表明,由光致荧光谱(PL)测量结果计算得到的响应波长与实际器件的响应波长有良好的一致性。     

InxGa1−xAs/InP quantum well structures grown on [111]B InP

We report growth and characterization details of lattice matched and coherently strained In_xGa_1−xAs/InP quantum well structures grown on misoriented [111]B InP substrates. Photoluminescence from a range of such structures, grown on substrates with optimum misorientation, show linewidths as good or better than equivalent [100] layers. Multiquantum well (MQW) samples with relatively modest compressive strain show X-ray diffraction data characteristic of highly uniform pseudomorphic quantum wells. With increased strain (x = 0.63), relaxation is evident through a degradation of the diffracted peak widths and through the observation of defects in the surface morphology. Fabricated strained p-i(MQW)-n diode structures exhibit low reverse leakage current densities (e.g. j = 6 μA/cm²). Room temperature photocurrent measurements on these devices show a strong excitonic blue shift (15 nm) with applied bias, as a consequence of the built-in piezoelectric field. The rate of peak shift, up to 8 nm/V, demonstrates excellent potential for low voltage optical modulator applications at around 1.55 μm wavelength.