Room-temperature operating extended short wavelength infrared photodetector based on interband transition of InAsSb/GaSb quantum well

Here in this paper,we report a room-temperature operating infrared photodetector based on the interband transition of an In As Sb/Ga Sb quantum well.The interband transition energy of 5-nm thick In As_(0.91)Sb_(0.09) embedded in the Ga Sb barrier is calculated to be 0.53 e V(2.35μm),which makes the absorption range of In As Sb cover an entire range from short-wavelength infrared to long-wavelength infrared spectrum.The fabricated photodetector exhibits a narrow response range from 2.0μm to 2.3μm with a peak around 2.1μm at 300 K.The peak responsivity is 0.4 A/W under-500-m Vapplied bias voltage,corresponding to a peak quantum efficiency of 23.8%in the case without any anti-reflection coating.At 300 K,the photodetector exhibits a dark current density of 6.05×10~(-3)A/cm~2under-400-m V applied bias voltage and3.25×10~(-5)A/cm~2under zero,separately.The peak detectivity is 6.91×10~(10)cm·Hz~(1/2)/W under zero bias voltage at 300 K.     

GaSb-based type-Ⅰ quantum well cascade diode lasers emitting at nearly 2-μm wavelength with digitally grown AlGaAsSb gradient layers

We report a Ga Sb-based type-I quantum well cascade diode laser emitting at nearly 2-μm wavelength. The recycling of carriers is realized by the gradient Al Ga As Sb barrier and chirped Ga Sb/Al Sb/In As electron injector. The growth of quaternary digital alloy with a gradually changed composition by short-period superlattices is introduced in detail in this paper. And the quantum well cascade laser with 100-μm-wide, 2-mm-long ridge generates an about continuous-wave output of 0.8 W at room temperature. The characteristic temperature T0 is estimated at above 60 K.     

Numerical study of strained InGaAs quantum well lasers emitting at 2.33 μm using the eight-band model

We investigate the band structure of a compressively strained In(Ga)As/In 0.53 Ga 0.47 As quantum well (QW) on an InP substrate using the eight-band k · p theory.Aiming at the emission wavelength around 2.33 μm,we discuss the influences of temperature,strain and well width on the band structure and on the emission wavelength of the QW.The wavelength increases with the increase of temperature,strain and well width.Furthermore,we design an InAs /In 0.53 Ga 0.47 As QW with a well width of 4.1 nm emitting at 2.33 μm by optimizing the strain and the well width.     

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.     

Optimized Optomechanical Micro-Cantilever Array for Uncooled Infrared Imaging

We present a new substrate-free bimaterial cantilever array made of SiN_x and Au for an uncooled micro-optomechanical infrared imaging device. Each cantilever element has an optimized deformation magnification structure. A160×160 array with a 120μm×120μm pitch is fabricated and an optical readout is used to collectively measure deflections of all microcantilevers in the array. Thermal images of room-temperature objects with higher spatial resolution have been obtained and the noise-equivalent temperature difference of the fabricated focal plane arrays is given statistically and is measured to be about 270mK.     

A method to extend wavelength into middle-wavelength infrared based on InAsSb/(Al)GaSb interband transition quantum well infrared photodetector

We present a method to extend the operating wavelength of the interband transition quantum well photodetector from an extended short-wavelength infrared region to a middle-wavelength infrared region. In the modified In As Sb quantum well, Ga Sb is replaced with Al Sb/Al Ga Sb, the valence band of the barrier material is lowered, the first restricted energy level is higher than the valence band of the barrier material, the energy band structure forms type-II structure. The photocurrent spectrum manifest that the fabricated photodetector exhibits a response range from 1.9 μm to 3.2 μm with two peaks at 2.18 μm and 3.03 μm at 78 K.     

A review on MBE-grown HgCdSe infrared materials on GaSb(211)B substrates

We review our recent efforts on developing HgCdSe infrared materials on Ga Sb substrates via molecular beam epitaxy(MBE) for fabricating next generation infrared detectors with features of lower production cost and larger focal plane array format size. In order to achieve high-quality HgCdSe epilayers, ZnTe buffer layers are grown before growing HgCdSe, and the study of misfit strain in ZnTe buffer layers shows that the thickness of ZnTe buffer layer needs to be below 300 nm in order to minimize the generation of misfit dislocations. The cut-off wavelength/alloy composition of HgCdSe materials can be varied in a wide range by varying the ratio of Se/Cd beam equivalent pressure during the HgCdSe growth.Growth temperature presents significant impact on the material quality of HgCdSe, and lower growth temperature leads to higher material quality for HgCdSe. Typically, long-wave infrared HgCdSe(x = 0.18, cut-off wavelength of 10.4 μm at 80 K) presents an electron mobility as high as 1.3×10~5cm~2·V~(-1)·s~(-1), a background electron concentration as low as 1.6×10~(16)cm~(-3), and a minority carrier lifetime as long as 2.2 μs. These values of electron mobility and minority carrier lifetime represent a significant improvement on previous studies of MBE-grown HgCdSe reported in the open literatures,and are comparable to those of counterpart HgCdTe materials grown on lattice-matched CdZnTe substrates. These results indicate that HgCdSe grown at the University of Western Australia, especially long-wave infrared can meet the basic material quality requirements for making high performance infrared detectors although further effort is required to control the background electron concentration to below 10~(15)cm~(-3). More importantly, even higher quality HgCdSe materials on GaSb are expected by further optimizing the growth conditions, using higher purity Se source material, and implementing postgrowth thermal annealing and defect/impurity gettering/filtering. Our results demonstrate the great potential of HgCdSe infrared materials grown on GaSb substrates for fabricating next generation infrared detectors with features of lower cost and larger array format size.     

Quantum dot quantum cascade photodetector using a laser structure

We report on a quantum dot quantum cascade detector(QD-QCD), whose structure is derived from a QD cascade laser. In this structure, more ordered In As QD layers formed in the Stranski–Krastanow growth mode on a thin Ga As buffer layer are incorporated into the active region. This QD-QCD can operate up to room temperature with a peak detection wavelength of 5.8 μm. A responsivity of 3.1 mA/W at 160 K and a detectivity of 3.6 × 10~8 Jones at 77 K are obtained. The initial performance of the detector is promising, and, by further optimizing the growth of InA s QDs, integrated QD-quantum cascade laser/QCD applications are expected.     

Influence of the abdominal wall on the nonlinear propagation of focused therapeutic ultrasound

This article theoretically studies the influence of inhomogeneous abdominal walls on focused therapeutic ultrasound based on the phase screen model. An inhomogeneous tissue is considered as a combination of a homogeneous medium and a phase aberration screen. Variations of acoustic parameters such as peak positive pressure, peak negative pressure, and acoustic intensity are discussed with respect to the phase screen statistics of human abdominal walls. Results indicate that the abdominal wall can result in energy loss of the sound in the focal plane. For a typical human abdominal wall with correlation length of 7.9~mm and variance of 0.36, the peak acoustic intensity radiated from a 1~MHz transmitter with a radius of 30~mm can be reduced by about 14% at the focal plane.     

The effects of InGaN layer thickness on the performance of InGaN/GaN p-i-n solar cells

InGaN/GaN p-i-n solar cells, each with an undoped In0.12Ga0.88N absorption layer, are grown on c-plane sapphire substrates by metal-organic chemical vapor deposition. The effects of the thickness and dislocation density of the absorp- tion layer on the collection efficiency of InGaN-based solar cells are analyzed, and the experimental results demonstrate that the thickness of the InGaN layer and the dislocation density significantly affect the performance. An optimized InGaN- based solar cell with a peak external quantum efficiency of 57% at a wavelength of 371 nm is reported. The full width at half maximum of the rocking curve of the （0002） InGaN layer is 180 arcsec.     

Wet etching and passivation of GaSb-based very long wavelength infrared detectors

The etching and passivation processes of very long wavelength infrared (VLWIR) detector based on the InAs/GaSb/AlSb type-II superlattice have been studied. By studying the effect of each component in the citric acid solution (citric acid, phosphoric acid, hydrogen peroxide, deionized water), the best solution ratio is obtained. After comparing different passivation materials such as sulfide + SiO₂, Al₂O₃, Si₃N₄ and SU8, it is found that SU8 passivation can reduce the dark current of the device to a greater degree. Combining this wet etching and SU8 passivation, the R₀A of VLWIR detector with a mesa diameter of 500 μm is about 3.6 Ω ·cm² at 77 K.     

320 × 256 Short-/Mid-Wavelength dual-color infrared focal plane arrays based on Type-II InAs/GaSb superlattice

Short-/Mid-Wavelength dual-color infrared focal plane arrays based on Type-II InAs/GaSb superlattice are demonstrated on GaSb substrate. The material is grown with 50% cut-off wavelength of 2.9 μm and 5.1 μm for the blue channel and red channel, separately at 77 K. 320 × 256 focal plane arrays fabricated in this wafer is characterized. The peak quantum efficiency without antireflective coating is 37% at 1.7 μm under no bias voltage and 28% at 3.2 μm under bias voltage of 130 mV. The peak specific detectivity are 1.51 × 10¹² cm·Hz^1/2/W at 2.5 μm and 6.11x10¹¹ cm·Hz^1/2/W at 3.2 μm. At 77 K, the noise equivalent difference temperature presents average values of 107 mK and 487 mK for the blue channel and red channel separately.     

表面绝缘混合平面丝阵Z箍缩激光阴影图像诊断

基于脉冲半高全宽约为9 ns、波长为532 nm的Nd:YAG激光器,采用条纹相机和商用数码相机两种记录设备,建立了时间分辨和时间积分两种模式的激光阴影图像诊断系统,在"强光一号"装置上对表面绝缘混合平面丝阵Z箍缩等离子体开展了实验研究.实验结果表明:在融蚀过程中表面绝缘金属丝冕等离子体发展较普通金属丝慢,在t=44ns到t=56ns之间,其平均膨胀速度分别为1.1×104m·s-1和1.7×104m·s-1;在等离子体滞止前10 ns的快速聚爆过程中,表面绝缘金属丝和普通金属丝两侧的平均聚爆速度分别为5.5×105m·s-1和9.3×105m·s-1,表面绝缘一侧等离子体滞止时间小于普通金属丝一侧,分别为5.9 ns和9.5 ns;等离子体碰撞分界线偏向于表面绝缘一侧,滞止时形成的磁流体不稳定性结构类似.     

Manufacturability of type-II InAs/GaSb superlattice detectors for infrared imaging

Type-II InAs/GaSb superlattice detectors and focal plane arrays (FPAs) with cut-off wavelength at 5.1 μm have been studied. For single pixel devices, dark current densities of 1 × 10⁻⁶ A/cm² and quantum efficiencies of 53% were measured at 120 K. From statistics of manufactured FPAs, an average FPA operability of 99.87% was observed. Furthermore, average temporal and spatial noise equivalent temperature difference (NETD) values of 12 mK and 4 mK, respectively, were deduced. Excellent stability of FPAs after non-uniformity correction was observed with no deterioration of the ratio between spatial and temporal noise during a two hour long measurement. Also after several cooldowns the ratio between spatial and temporal NETD stayed below 0.6.     

InAs/GaSb superlattice focal plane arrays for high-resolution thermal imaging

The first fully operational mid-IR (3–5 μm) 256×256 IR-FPA camera system based on a type-II InAs/GaSb short-period superlattice showing an excellent noise equivalent temperature difference below 10 mK and a very uniform performance has been realized. We report on the development and fabrication of the detecor chip, i.e., epitaxy, processing technology and electro-optical characterization of fully integrated InAs/GaSb superlattice focal plane arrays. While the superlattice design employed for the first demonstrator camera yielded a quantum efficiency around 30%, a superlattice structure grown with a thicker active layer and an optimized V/III BEP ratio during growth of the InAs layers exhibits a significant increase in quantum efficiency. Quantitative responsivity measurements reveal a quantum efficiency of about 60% for InAs/GaSb superlattice focal plane arrays after implementing this design improvement. The paper presented there appears in Infrared Photoelectronics, edited by Antoni Rogalski, Eustace L. Dereniak, Fiodor F. Sizov, Proc. SPIE Vol. 5957, 595707 (2005).     

TPV系统热辐射发电模块数值分析

建立TPV系统热辐射发电模块的数理模型,通过数值模拟获得SiC辐射器分别配合GaSb和Si电池所构成的TPV系统的输出伏安特性曲线;以GaSb电池为例,分别分析SiC辐射器温度和电池温度对系统性能的影响,得出如下结论:辐射器温度升高,系统输出电能密度迅速增大,电池效率稳步提高,辐射器温度从1400 K升至1900 K,系统输出电能密度从0.67 W·cm^-2增至5.43 W·cm^-2,电池效率从16.3%上升到24.8%;电池温度升高导致系统性能下降,电池温度每升高10 K,系统输出电能密度减少约0.15 W·cm^-2,电池效率也大幅下降.最后讨论与GaSb匹配的一种选择性辐射器的辐射能量分布情况,与SiC辐射器相比,选择性辐射器可以显著减少辐射能量中的不可用部分,从而有效提高系统的性能与稳定性.     

Performance of dual-band short-or mid-wavelength infrared photodetectors based on InGaAsSb bulk materials and InAs/GaSb superlattices

In this paper,we demonstrate bias-selectable dual-band short-or mid-wavelength infrared photodetectors based on In_(0.24)Ga_(0.76)As_(0.21)Sb_(0.79)bulk materials and InAs/GaSb type-II superlattices with cutoff wavelengths of 2.2μm and 3.6μm,respectively.At 200 K,the short-wave channel exhibits a peak quantum efficiency of 42%and a dark current density of5.93×10~(-5)A/cm~2at 500 mV,thereby providing a detectivity of 1.55×10~(11)cm·Hz~(1/2)/W.The mid-wave channel exhibits a peak quantum efficiency of 31%and a dark current density of 1.22×10~(-3)A/cm~2at-300 mV,thereby resulting in a detectivity of 2.71×10~(10)cm·Hz~(1/2)/W.Moreover,we discuss the band alignment and spectral cross-talk of the dual-band n-i-p-p-i-n structure.     

Mid-wavelength type II InAs/GaSb superlattice infrared focal plane arrays

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 SiN_x 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.     

退火对Pb辐照Al2O3单晶发光特性的影响

研究了230MeV的²⁰⁸Pb²⁷⁺辐照Al₂O₃样品及随后在600,900,1100K高温条件下退火后的光致发光特性。从辐照样品的测试结果可以清楚地看到在波长为390,450nm处出现了强的发光峰。辐照量为1×10¹³ions/cm²时,样品的发光峰最强。经过600K退火2h后测试结果显示,380nm发光峰剧烈增强,而其他发光峰显示不明显。在900K退火条件下,380nm的发光峰开始减弱,而在360,510nm出现了明显的发光峰,至到1100K退火完毕后380nm的发光峰完全消失,而360,510nm的发光峰相对增强。从被辐照样品的FTIR谱中看到,波数在460~510cm^-1间的吸收是振动模式,经过离子辐照后,吸收带展宽,随着辐照量的增大,Al₂O₃振动吸收峰消失,说明Al₂O₃振动模式被完全破坏。1000~1300cm^-1之间为Al—O—Al桥氧的伸缩振动模式,辐照后吸收带向高波数方向移动,说明其振动模式受到影响。辐照剂量较小的样品,损伤程度相对较低,经退火晶化后,振动模式基本恢复到单晶状态;辐照剂量较高的样品,损伤程度大,退火处理后表面变得较粗糙,振动模式并未出现,说明结构破坏严重。