高倍增低暗电流AlInAsSb四元数字合金雪崩光电二极管

用分子束外延系统(MBE)生长高质量GaSb基AlInAsSb四元数字合金制作雪崩光电二极管(APD).为了克服随机体材料生长方式发生的偏析现象,采用迁移增强的数字合金生长方式,其快门顺序为AlSb,AlAs,AlSb,Sb,In,InAs,In,Sb.其高分辨率X射线衍射(HRXRD)曲线显示出尖锐的卫星峰,并显示出...     

超晶格雪崩光电二极管

报道了超晶格雪崩光电二极管的工作原理,结构,特性及其制造工艺。     

超晶格雪崩光电二极管

报道了超晶格雪崩光电二极管的工作原理、结构、特性及其制造工艺。     

级联倍增InAlAs/InAlGaAs雪崩光电二极管暗电流成分分析

实验制备了级联倍增InAlAs/InAlGaAs雪崩光电二极管,对二极管暗电流随台面直径和温度的变化进行了研究分析。结合暗电流函数模型,利用Matlab软件对暗电流的各成分进行了数值计算,并仿真研究了芯片结构的缺陷浓度Nt和表面复合速率S对暗电流的影响。结果表明,二极管暗电流主要来自于体暗电流,而非表面漏电流。在工作点偏压90V处,受缺陷影响的缺陷辅助隧穿电流Itat在暗电流中占据了主导,并推算出了芯片结构的缺陷浓度Nt约为1019 m-3、吸收区中的缺陷浓度NInGaAs约为7×1015 m-3。由于芯片结构的缺陷主要来源于InAlAs/InAlGaAs倍增区和InGaAs吸收区,而吸收区缺陷占比很少,因此认为缺陷主要来自于异质结InAlAs/InAlGaAs倍增区。     

InGaAs/InP雪崩光电二极管暗电流机理研究

基于InGaAs/InP雪崩光电二极管,讨论吸收层厚度和少子寿命以及倍增层厚度和少子寿命对暗电流的影响。研究表明,吸收层厚度影响热产生复合(shockley-read-hall, SRH)和缺陷辅助隧穿(trap-assisted tunneling, TAT)暗电流大小,而倍增层厚度则对TAT和直接隧穿(band-band tunneling, BBT)暗电流影响较大。少子寿命可以等效为缺陷的影响,因而对与缺陷相关的SRH和TAT暗电流影响较大。对暗电流机理的分析,为研究低暗电流高信噪比的雪崩器件提供良好的理论预测。     

雪崩光电器件过剩噪声分析

基于光子在雪崩光电器件内吸收位置的差异,提出过剩噪声因子在器件垂直方向的分布模型,并基于TCAD 和Matlab 仿真,验证了模型的有效性。模型考虑了光子在硅雪崩器件内不同吸收位置的过剩噪声因子,结合光子在器件深度方向的吸收比例,计算器件(器件结构由TCAD构造)的平均噪声因子水平:233 @ E=34×105 V/cm 和534 @ E=36×105 V/cm,比单独考虑光子在N中性体区吸收(过剩噪声因子:288 @ E=34×105 V/cm 和1294 @ E=36×105 V/cm)或P中性体区吸收(过剩噪声因子:221 @ E=34×105 V/cm 和379 @E=36×105 V/cm),更能反映器件的真实工作情况。     

具有优化倍增层InAlAs/InGaAs雪崩光电二极管

通过优化倍增层的厚度,研究了InAlAs/InGaAs雪崩光电二极管增益带宽积和暗电流之间的关系。利用仿真计算得出200 nm厚的倍增层能够改善增益带宽积并降低暗电流。制成的InAlAs/InGaAs 雪崩光电二极管性能优异,与计算趋势一致。在获得0.85 A/W的高响应和155 GHz的增益带宽积的同时,器件暗电流低于19 nA。这项研究对雪崩光电二极管在未来高速传输的应用具有重要意义。     

长波长高速雪崩光电二极管的理论研究

本文以现有的理论研究和实验研究的结果为依据,提出了长波长高速及超高速雪崩光电二极管(APD)的两设计原则:一是在雪崩管内建立合理的电场强度分布;二是尽可能减少电寄生。这是得到高速或超高速响应、高量子效率以及低噪声性能的根本途径。     

具有超晶格雪崩区的电子倍增型雪崩光电二极管

基于碰撞离化理论研究设计了In0.53 Ga0.47 As/In0.52 Al0.48As电子倍增超晶格结构雪崩光电二极管,使用MOCVD外延得到实验片,经过工艺流片后进行封装测试.测试结果显示,具有超晶格雪崩区的电子倍增型APD器件,其暗电流可以控制在纳安级,光电流增益达到140,证明具有超晶格雪崩区的电子倍增型雪崩光电二极管具有很好的光电探测性能.     

多阳极雪崩光电二极管

由法国电信企业控股的Voxtel公司展出一系列固体硅光电倍增管。这些器件由一些紧凑的小面积多阳极雪崩光电二极管构成,其增益约为10^6,因此能探测单个光子。这些器件能以光子计数的水平探测弱光而对磁场不敏感。它们的应用包括荧光寿命成像、正电子放射层析、核医学、高能物理、辐射探测、激光雷达、粒子粒度分析、DNA定序以及由激光诱导的荧光探测等。     

Low dark current GaN avalanche photodiodes

We report the fabrication and characterization of GaN avalanche photodiodes grown on sapphire by metalorganic chemical vapor deposition. Current-voltage characteristics indicate a gain higher than 23. The photoresponse is independent of the bias voltage prior to the onset of avalanche gain which occurs at an electric field of ~4 MV/cm. Near avalanche breakdown, the dark current of a 30-μm diameter device is less than 100 pA. The breakdown shows a positive temperature coefficient of 0.03 V/K that is characteristic of avalanche breakdown     

Study of reverse dark current in 4H-SiC avalanche photodiodes

Temperature-dependent current-voltage (I-V) measurements have been used to determine the reverse dark current mechanisms in 4H-SiC avalanche photodiodes (APDs). A pn junction vertical mesa structure, passivated with SiO/sub 2/ grown by plasma enhanced chemical vapor deposition, exhibits predominate leakage current along the mesa sidewall. Similar APDs, passivated by thermal oxide, exhibit lower dark current before breakdown; however, when the temperature is higher than 146/spl deg/C, an anomalous dark current, which increases rapidly with temperature, is observed. This current component appears to be eliminated by the removal of the thermal oxide. Near breakdown, tunneling is the dominant dark current mechanism for these pn devices. APDs fabricated from a pp/sup -/n structure show reduced tunneling current. At room temperature, the dark current at 95% of breakdown voltage is 140 fA (1.8 nA/cm/sup 2/) for a 100-/spl mu/m diameter APD. At a gain of 1000, the dark current is 35 pA (0.44 /spl mu/A/cm/sup 2/).     

A model for dark current and multiplication in HgCdTe avalanche photodiodes

In this paper we report the calculated results of the dark current and multiplication factor in MBE grown HgCdTe avalanche photodiodes with separate absorption and multiplication (SAM-APD). The device architecture used for this analysis comprises the following layers: p⁺ contact, p junction, n⁻ multiplication, n charge sheet, n⁻ absorber, and n⁺ contact. Various leakage current mechanisms are considered and the generation-recombination term is found to be the dominant one for this device structure. However, experimental reverse bias I-V characteristics reported earlier by T. de Lyon et al. shows a large deviation from ideality, which can not be explained in terms of bulk leakage current mechanism. To explain the large difference between experimental and theoretical data we consider that the dominant generation-recombination current is multiplied through impact ionization process. To validate this assumption, multiplication is calculated as a function of reverse bias. Electric field profile is obtained and the multiplication is computed using the ionization coefficients and avalanche gain equations. Breakdown voltage is found to be 85 V for room temperature operation in agreement with available data in the literature. The theoretical I-V curves considering multiplication are compared with the experimental ones and a close agreement is found which validate this model.     

Low dark current InGaAs PIN photodiodes grown by molecular beam epitaxy

High-quality InGaAs PIN photodiodes have been made from high-purity layers grown on InP substrate by molecular beam epitaxy. The diodes are top-illuminated mesa-type passivated and planarised by polyimide. The devices exhibit dark current densities as low as 2.3 × 10?5 A/cm2 at ?10 V with a breakdown voltage of ?80 V. These values are comparable with those obtained by other more conventional growth techniques, and are the best so far reported by MBE.     

High sensitivity organic photodiodes with low dark currents and increased lifetimes

Organic semiconductors hold the promise for large-area, low-cost image sensors and monolithically integrated photonic microsystems. This requires the availability of photodiodes offering at the same time high quantum efficiency, low noise and long lifetimes. Although published structures of organic photodiodes offer high external quantum efficiencies (EQE) of up to 76% [F. Padinger, R.S. Rittberber, N.S. Sariciftci, Effects of postproduction treatment on plastic solar cells, Advanced Functional Materials 13 (2003) 1, P. Schilinsky, C. Waldauf, C.J. Brabec, Recombination loss analysis in polythiophene based bulk heterojunction photodetectors, Applied Physics Letters 81 (20) (2002) 3885], [1], [2] they normally suffer from short lifetimes of only a few hundred hours as well as large dark currents. In our work the lifetime of a poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) heterojunction photodiode structure was increased to several thousand hours by omitting the widely used poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) anode layer. In addition, a simple model of optical interference and absorption effects was used to find the optimum thickness that combines high quantum efficiency with low dark current. As a result, we report on organic photodiodes with state-of-the-art EQE of 70% at 0 V bias, an on/off current ratio of 10⁶ at −1 V and 40 mW/cm² illumination, dark current densities below 10 nA/cm² at −1 V, and a lifetime of at least 3000 h.     

InP/InGaAsP/InGaAs avalanche photodiodes grown by chemical beam epitaxy

InP/InGaAsP/InGaAs avalanche photodiodes with separate absorption, grading, and multiplication regions (SAGM-APD's) have been fabricated from wafers grown by chemical beam epitaxy (CBE). These APD's exhibit low dark current (<25 nA at 90 percent of breakdown), low capacitance (≈0.2 pF), and good responsivity (0.75 A/ W at 1.3 µm). The pulse response, which is relatively independent of avalanche gain, is characterized by rise and fall times of approximately 1.4 ns.     

Mean gain of avalanche photodiodes in a dead space model

Based on a first order expansion of the recursive equations, we derive approximate analytical expressions for the mean gain of avalanche photodiodes accounting for dead space effects. The analytical solutions are similar to the popular formula first obtained in local approximation, provided that the ionization coefficients, α and β, are replaced with suitable effective ionization coefficients depending on dead space. The approximate solutions are in good agreement with the exact numerical solutions of the recursive equations for p-i-n devices as well as for photodiodes with nonconstant electric field profile. We also show that dead space causes non negligible differences between the values of the effective ionization coefficients entering in carrier continuity equations, the carrier ionization probability per unit length and the ionization coefficients derived by experimenters from multiplication measurements     

Effect of dead space on gain and noise ofdouble-carrier-multiplication avalanche photodiodes

The effect of dead space on the statistics of the gain in a double-carrier-multiplication avalanche photodiode (APD) is determined using a recurrence method. The dead space is the minimum distance that a newly generated carrier must travel in order to acquire sufficient energy to become capable of causing an impact ionization. Recurrence equations are derived for the first moment, the second moment, and the probability distribution function of two random variables that are related, in a deterministic way, to the random gain of the APD. These equations are solved numerically to produce the mean gain and the excess noise factor. The presence of dead space reduces both the mean gain and the excess noise factor of the device. This may have a beneficial effect on the performance of the detector when used in optical receivers with photon noise and circuit noise     

High-speed InP/InGaAs avalanche photodiodes with a compositionallygraded quaternary layer

InP/InGaAs avalanche photodiodes (APDs) with a compositionally graded quaternary layer at the heterointerface between the InGaAs absorption and InP multiplication regions were fabricated and tested. A comparison of samples with the graded layer and with conventional three quaternary layers showed that the frequency characteristics for samples with the graded layer did not deteriorate at a low bias voltage even below -100°C, unlike APDs with three InGaAsP layers. Thus, no hole trapping occurred at the InP/InGaAs heterointerface with the graded layer. A sample with the graded layer showed a cutoff frequency exceeding 9 GHz at a low multiplication factor of 2. The authors found InP/InGaAs APDs with the compositionally graded quaternary layer to be useful over a wide temperature range     

Solution processed small molecule organic interfacial layers for low dark current polymer photodiodes

We demonstrate a small molecule solution processed hole interfacial layer approach to improve the dark current characteristics of polymer photodiodes. The two hole blocking materials under investigation 3-phenyl-4(1′-naphthyl)-5-phenyl-1,2,4-triazole (TAZ) and 2-[3,5-bis(1-phenylbenzimidazol-2-yl)phenyl]-1-phenylbenzimidazole (TPBi) are spincoated from ethanol as an orthogonal solvent on top of a P3HT:PCBM active layer. We reduce the dark current at a bias voltage of −1 V by a factor of 17.2 by introducing a TAZ interfacial layer while keeping the responsivity unchanged.