Waveguided Ge/Si Avalanche Photodiode With Separate Vertical SEG-Ge Absorption, Lateral Si Charge, and Multiplication Configuration

A novel Si-waveguide-integrated Ge/Si avalanche photodiode (APD) is demonstrated for the first time, in which light propagating along the Si waveguide is evanescently absorbed by an overlaying Ge layer selectively grown on it, whereas the avalanche multiplication of photoexcited carriers occurs laterally in the Si-waveguide layer. The APD provides a responsivity of $sim$7.2 A/W at 1550 nm, which is $sim$26 times larger than the corresponding vertical Ge/Si p-i-n photodiode, and exhibits a 3-dB bandwidth of $sim$3.3 GHz, a dark current of $sim!hbox{22} muhbox{A}$ at 22-V bias, and an excess noise factor of $sim$4, respectively.      

High-Efficiency p-i-n Photodetectors on Selective-Area-Grown Ge for Monolithic Integration

We demonstrate normal incidence p-i-n photodiodes on selective-area-grown Ge using multiple hydrogen annealing for heteroepitaxy for the purpose of monolithic integration. An enhanced efficiency in the near-infrared regime and the absorption edge shifting to longer wavelength is achieved due to 0.14% residual tensile strain in the selective-area-grown Ge. The responsivities at 1.48, 1.525, and 1.55 $mu hbox{m}$ are 0.8, 0.7, and 0.64 A/W, respectively, without an optimal antireflection coating. These results are promising toward monolithically integrated on-chip optical links and in telecommunications.      

Low-Voltage High-Speed (18 GHz/1 V) Evanescent-Coupled Thin-Film-Ge Lateral PIN Photodetectors Integrated on Si Waveguide

This letter presents the device performance of scaled thin-film-Ge lateral PIN photodetectors integrated on a Si waveguide. The photodetectors are with closely spaced p$^{+}$/n$^{+}$ regions (0.8 $mu$m) on a Ge region with short length (5–20 $mu$ m) and narrow width (2.4 $mu$m). Though with a thin Ge layer (${sim}$220 nm including bottom SiGe buffer), light is evanescent-coupled from the Si waveguide effectively to the overlying Ge detector. The device exhibits ${f}_{3 {rm dB}}$ bandwidth of 18 GHz with external responsivity of 0.13 A/W for 1550 nm at ${-}$1 V. Considering the coupling loss and waveguide loss, the internal responsivity is as high as 0.65 A/W. It is shown that with increasing detector length, the devices' internal quantum efficiency can be improved to ${sim}$ 90% and by suppressing parasitic effects, speed can be boosted further towards several tens of gigahertz.      

Low Dark Current GaN p-i-n Photodetectors With a Low-Temperature AlN Interlayer

GaN p-i-n ultraviolet (UV) photodetectors (PDs) with a low-temperature (LT)-AlN interlayer were proposed and fabricated. It was found that the dark current of such detectors is as small as 28pA even at a high reverse bias of 40 V. Although the high potential barrier at the AlN-GaN interface would slightly reduce the responsivity of PD under low reverse biases, the high UV-to-visible rejection ratio of the PD with an LT-AlN interlayer could be achieved under high reverse biases due to its very low dark current. The rejection ratio of the PD with the LT-AlN interlayer is as large as 735 at the reverse bias of 40 V.     

p-i-n结构GaN光电探测器性能的研究

近年来,可见盲与太阳盲光电探测器在火灾监控、太空通信和导弹尾焰探测等方面的应用引起了越来越多的关注。由于氮化镓(GaN)是直接宽带隙半导体材料,所以成为了在可见区与紫外区的光电器件的首选材料,而p-i-n结构的器件因其响应度高、暗电流低、便于集成等优点倍受人们的青睐。采用金属有机气相外延(MOCVD)法制备了p-i-n结构的GaN紫外光电探测器。在此基础上,采用N2气氛下热退火处理的方法,提高了p型GaN层的载流子浓度,从而降低了器件的暗电流。器件在1 V偏压下,暗电流仅为65 pA。器件在1 V偏压下的最大响应度值出现在361 nm处,大小为0.92 A/W。     

GaN基p-i-n结构紫外光探测器

用反应分子束外延(RMBE)方法在蓝宝石衬底上制备了GaN p-i-n结构,应用常规的半导体工艺制成了紫外光探测器,测试结果显示其正向导通电压为4.6 V,反向击穿电压大于40 V;室温下反偏3 V时的暗电流为6.68 pA,峰值响应度0.115 A/W出现在367 nm处;400 nm处的响应度为6.59×10-5A/W,比峰值响应度低四个量级.     

Performance of Ge-on-Si p-i-n Photodetectors for Standard Receiver Modules

Ge on Si p-i-n photodetectors with areas which are compatible with commercially available receivers have been fabricated and tested. A dark current density of 6 mA/cm² at -1-V bias has been measured at room temperature; when heated to 85 degC, the measured dark current increases by a factor of nine. A responsivity of 0.59 A/W at 850 nm has been measured from these Ge detectors, which matches or exceeds commercially available GaAs devices. We have measured bandwidths approaching 9 GHz at -2-V bias from 50-mum diameter Ge detectors, and have observed eye diagrams comparable to those obtained from GaAs-based receivers at 4.25 Gb/s     

基于氮化镓单晶的垂直p-i-n二极管性能研究

利用高质量自支撑GaN衬底,通过外延方法制备了垂直结构的GaN基p-i-n型二极管结构.通过对材料结构、杂质浓度分布以及对器件整流特性的研究,探究了影响垂直结构器件特性的关键因素.结果 表明,在同质外延的制备过程中,衬底表面的粗糙程度将使制备的环形结构具有不规则形状,这种不规则电极对垂直结构器件的性能将产生不利影响;此外,多种杂质在界面处聚集,进而形成平面漏电通道,是降低器件耐压值的主要因素.     

Impact of Local Strain From Selective Epitaxial Germanium With Thin Si/SiGe Buffer on High-Performance p-i-n Photodetectors With a Low Thermal Budget

This letter reports on the impact of selective epitaxial germanium, specifically its local strain effects, on high-performance p-i-n photodetectors for near-infrared applications. By combining a thin compliant Si epitaxial layer (~6 nm) with SiGe buffer (10-15 nm), we demonstrated a high-quality Ge film (~150 nm) prepared by two-step growth. Without using high-temperature cyclic anneal, Ge films with smooth surface (root mean square = ~ 0.67 nm) and low dislocation density (4 x 10⁶ cm^-2) have been produced. The Si buffer locally enhances the tensile strain (epsiv = 0.63%) in Ge while slightly suppressing the dark current by half to 0.12 muA (with circular ring area = 1230 mum² and spacing = 2 mum). A lateral p-i-n Ge photodetector has been demonstrated with enhanced photoresponse of ~190 mA/W at 1520 nm and a 3-dB bandwidth of 5.2 GHz at 1 V.     

多量子阱红外探测器垂直光耦合研究

对多量子阱红外探测器制作中GaAs衬底减薄工艺程序进行了研究与讨论.通过将器件压焊封装进杜瓦瓶中,测量其室温和低温条件下,I-V特性,以及在低温条件下的器件信噪比,并以傅里叶变换红外光谱仪对器件进行光谱测量,得到光电流谱,从而比较了将器件衬底磨45.斜角的边耦合情况,以及直接将衬底减薄至(29±2)μm两种情况下器件的性能.并讨论了减薄材料在垂直入射情况下仍能引起器件光吸收的主要原因.结果表明,由于GaAs材料的各向异性,湿法腐蚀会使器件台面形成正梯形和倒梯形结构,其作用等同于器件磨至45°斜角,因此在垂直入射时器件也会有光电流产生.此外,在衬底进行减薄抛光后,衬底会有很小的起伏,这也可能引起光耦合,从而产生光电流.     

近红外波段Ge光电探测器的研究进展

随着光通信技术的发展,如何制备能与Si基电路单片集成的响应波长在1.3和1.55 μm的高性能光电探测器成为研究热点.总结了SiGe组分变化的缓冲层技术、低温缓冲层技术以及选区外延这三种主流的Ge材料外延技术,介绍了pin结构、金属-半导体-金属(MSM)结构、雪崩光电二极管(APD)结构以及pin结构和MSM结构与光波导集成这四种不同结构的Ge光电探测器,并从这些不同结构的器件制备技术方面阐述了近红外波段Ge光电探测器的研究进展及其应用.     

石墨烯与典型光导型光电探测器读出电路的对比研究

石墨烯光电探测器具有兼容性好和宽波段响应等优势,其读出电路可类似于微测辐射热计等传统探测器.然而,石墨烯光电探测器一般属于光子型,其响应度、功耗和积分时间等具有显著差异.针对纯石墨烯、石墨烯-硫化铅异质结、硫化铅和典型微测辐射热计4种探测器,结合实测器件参数,进行读出电路的对比研究.仿真结果表明:由于其较高的响应度,实...     

Temperature-Dependence of Ge on Si p–i–n Photodetectors

We investigate the temperature dependence of germanium on silicon p–i–n photodetectors in terms of both dark current density and near-infrared responsivity. The dark current increases by nearly a factor 1.6 every 10 $^{circ} $C, consistently with carrier generation in the space charge region. The responsivity has a complex trend, its temperature variation depending on wavelength and on the germanium quality. Detectors with a large defect density in the active layer exhibit a reduced responsivity as the temperature increases.      

Lateral photoconductivity of Ge/Si heterostructures with Ge quantum dots

The spectral dependences of the lateral photoconductivity of Ge/Si heterostructures with Ge quantum dots are studied. The photoresponse of the Ge/Si structures with Ge nanoclusters is detected in the range 1.0–1.1 eV at T = 290 K, whereas the photocurrent in the single-crystal Si substrate is found to be markedly suppressed. This result can be attributed to the effect of elastic strains induced in the structure on the optical absorption of Si. At temperatures below 120 K, the heterostructures exhibit photosensitivity in the spectral range 0.4–1.1 eV, in which the Si single crystal is transparent. The photocurrent in this range is most likely due to the transitions of holes from the ground states localized in the quantum dots to the extended states of the valence band.     

High-performance p-i-n Ge on Si photodetectors for the nearinfrared: from model to demonstration

We have investigated the integration of Ge p-i-n and n-i-p heterojunction photodiodes on Si. Recognizing the crucial role of interface defects at the Ge-Si interface on the performance of photodetectors, we have designed and fabricated high-performance n-i-p Ge photodiodes on p⁺-Si substrates. These photodiodes exhibit short-circuit responsivities of 0.3 and 0.2 A/W at 1.3 and 1.55 μm, respectively, reverse dark currents of 20 mA/cm² and response times of 800 ps     

Lateral photoconductivity of multilayer Ge/Si structures with Ge quantum dots

Spectra of lateral photoconductivity of multilayer Ge/Si structures with Ge quantum dots, fabricated by molecular-beam epitaxy are studied. The photoresponse caused by optical transitions between hole levels of quantum dots and Si electronic states was observed in the energy range of 1.1–0.3 eV at T = 78 K. It was shown that the electronic states localized in the region of Si band bending near the Ge/Si interface mainly contribute to lateral photoconductivity. The use of the quantum box model for describing hole levels of quantum dots made it possible to understand the origin of peaks observed in the photoconductivity spectra. A detailed energy-level diagram of hole levels of quantum dots and optical transitions in Ge/Si structures with strained Ge quantum dots was constructed.     

Interdigitated Ge p-i-n photodetectors fabricated on a Si substrate using graded SiGe buffer layers

We report an interdigitated p-i-n photodetector fabricated on a 1-/spl mu/m-thick Ge epitaxial layer grown on a Si substrate using a 10-/spl mu/m-thick graded SiGe buffer layer. A growth rate of 45 /spl Aring//s/spl sim/60 /spl Aring//s was achieved using low-energy plasma enhanced chemical vapor deposition. The Ge epitaxial layer had a threading dislocation density of 10/sup 5/ cm/sup -2/ and a rms surface roughness of 3.28 nm. The 3-dB bandwidth and the external quantum efficiency were measured on a photodetector having 1-/spl mu/m finger width and 2-/spl mu/m spacing with a 25/spl times/28 /spl mu/m/sup 2/ active area. At a wavelength of 1.3 /spl mu/m, the bandwidth was 2.2, 3.5, and 3.8 GHz at bias voltages of -1, -3, and -5 V, respectively. The dark current was 3.2 and 5.0 /spl mu/A at -3 and -5 V, respectively. This photodetector exhibited an external quantum efficiency of 49% at a wavelength of 1.3 /spl mu/m.     

单向载流子传输光电探测器模拟

用Atlas软件对单向载流子传输光电探测器(uni-traveling-carrier photodetector,UTC-PD)进行了模拟,研究了器件的基本工作原理,着重讨论了器件性能与外延层结构的关系.设计出的UTC-PD可同时具有高的响应度(≥0.18A/W)和宽的3dB带宽(≥100GHz).与传统的pin光电探测器相比简化了前端电路结构,降低了噪声,节约了成本,可以应用于超高速光互联.     

CVD金刚石薄膜紫外光探测器研究

金刚石薄膜紫外光探测器对紫外光有较高的灵敏度和良好的开关特性。本文讨论了该器件的光电流随入射光波长的变化和开关时间响应。实验证明,金刚石薄膜是一种良好的紫外光探测材料。