Afterpulsing model based on the quasi-continuous distribution of deep levels in single-photon avalanche diodes

We have performed a statistical characterization of the effect of afterpulsing in a free-running silicon single-photon detector by measuring the distribution of afterpulse waiting times in response to pulsed illumination and fitting it by a sum of exponentials. We show that a high degree of goodness of fit can be obtained for five exponentials, but the physical meaning of estimated characteristic times is dubious. We show that a continuous limit of the sum of exponentials with a uniform density between the limiting times gives excellent fitting results in the full range of the detector response function. This means that in certain detectors, the afterpulsing is caused by a continuous band of deep levels in the active area of the photodetector.     

InGaAs/InP中离子注入和新型HPT

ＩｎＧａＡｓ／ＩｎＰ是制作光电器件与微波器件的重要材料。离子注入ＩｎＧａＡｓ／ＩｎＰ做掺杂或制作高阻层是人们十分关注的研究课题。采用Ｆｅ＾＋注入ＩｎＧａＡｓ／ＩｎＰ得到了电阻率升高的好结果。用Ｂｅ＾＋注入制作了新结构ＨＰＴ的基区。研制成功了在１．５５μｍ波长工作的ＩｎＧａＡｓ／ＩｎＰ新结构光电晶体管,在０．３μＷ入射光条件下,光电增益为３５０。     

InP 层对正面及背面入光 PIN 探测器响应度影响研究

InP盖层对光的吸收及入射光在探测器多界面间的多次反射,使InP层对InGaAs/InPPIN探测器的响应度产生了很大的影响。本文测量了正面和背面入光PIN探测器的响应度,并与测量的InP晶片透射率及模拟的透射率进行比较,分析了InP层对正面及背面入光PIN探测器响应度的影响。结果表明,随着InP层厚度的增加,响应度峰与峰的间隔Δλ不断减小,波形越来越密集。所以正面入光探测器的响应度起伏比较明显,且随着InP层厚度的增加,响应度极值对应的波长发生红移。背面入光探测器的响应度非常密集而成为准连续的带状。     

InP/InGaAsHBT湿法化学选择腐蚀技术

用H3PO4:H2O2系和HCl系腐蚀液实现了InP对InGaAs、InGaAs对InP的湿法化学选择腐蚀,并将其应用于InP/InGaAsHBT制作,发射极面积为10μm×20μm的单管共发射极直流增益β为70,截止频率Ft和最大振荡频率Fmax分别为11GHz和12GHz.     

Optimization of growth of InGaAs/InP quantum wells using photoluminescence and secondary ion mass spectrometry

InGaAs/InP quantum wells of widths varying from 19 Å to 150 Å have been grown by MOVPE and the growth temperature optimized using photoluminescence and SIMS. It was thus found that for a 78 Å well the lowest PL linewidth of 12.7 meV at 12 K was obtained for growth at 625°C. SIMS also showed sharpest interfaces for this temperature compared with growth at 610°C and 640°C. The well widths determined from PL energies were in good agreement with a growth rate of 8.25 Å/s. However, while the barrier widths of 150 Å were in agreement with SIMS results, the well widths from SIMS were found to be much larger, due to a lower sputtering rate of InGaAs compared with InP. Quantitative comparison was made assuming the presence of InAsP and InGaAsP interface layers on either side of the wells and the relative sputtering rates determined.     

Crystallographic dependence of OMVPE InGaAs/InP lateral growth on patterned (100) InP substrates prepared by wet etching

InP layers and InP/InGaAs structures were grown at 600°C using OMVPE on non-planar wet-etch InP substrates with patterns aligned at various angles Θ within [010] and [01-1] as well as [001] and [0-11]. The patterns were 15-μm-high ordinary mesa-shaped ridges with the sidewall facet angle dependent on the alignment angle Θ. Within 0.5°<Θ<10°, the morphology of InP exhibited ledges running down the slope of the facet, which increased the surface roughness. For larger angles Θ, it exhibited different features. The nucleation of InGaAs proceeded through faceted trapezoidal features. This type of nucleation was not suppressed on the facets for 0.5°<Θ<10°. For larger Θ, the InGaAs morphology exhibited different features.     

Investigation of InP/InGaAs superlattice-emitter bipolar transistor with multiple negative-differential-resistance regions

The sequential tunneling behavior in InP/InGaAs superlattice-emitter bipolar transistors is demonstrated by theoretical analysis and experimental results. The tunneling mechanism in the InP/InGaAs superlattice structures is analyzed by theoretical calculation. Due to the weak coupled tunneling mechanism, the interesting multiple negative-differential-resistances (NDRs) resulting from the creation and extension of high-field domain in the superlattice are observed at room temperature. Experimentally, the transistor performances, including a high current gain of 454, a low collector–emitter offset voltage of 80 mV, and a pronounced multiple NDRs, are achieved. The proposed structures may provide good potential for signal amplifiers and multiple-valued logic circuit applications.     

Time-dependent photon number discrimination of InGaAs/InP avalanche photodiode single-photon detector

We investigated the photon-number-resolving (PNR) performance of the InGaAs/InP avalanche photodiode (APD) as a function of the electric gate width and the photon arrival time. The optimal electric gate width was around 1 ns for PNR measurements in our experiment, which provided a PNR capability up to three photons per pulse when the detection efficiency was ~20%. And the dependence of the PNR performance on the arrival time of the photons showed that the photon number could be better resolved if the photons arrived on the rising edge of the electric gate than on the falling edge. In addition, we found that with the increase of the electric gate width, PNR performance got worse. The observation would be helpful for improving the PNR performance of the InGaAs/InP APD in the gated mode.     

Analysis of a InGaAs/InP single photon detector at 1550 nm

A new type of single-photon detector is introduced and its related properties characterized. The single-photon detector operating in the Geiger mode uses a new type of cooling system to moderate temperature, which can make the temperature drop to ?65?°C. Besides, the single-photon detector adopts a hold-off time modulation feedback control circuit to decrease the afterpulsing effects and the gate pulse is coupled to the avalanche diode through capacitance. In addition, a suitable delay and comparator with latch function circuit are used to detect avalanche signals. Experimental conditions are that the clock frequency is 10 MHz, refrigeration temperature is ?65?°C, and the width of control pulse is 5 ns. The experimental results indicate that quantum efficiency is about 20.42% and the dark count rate is about 5 × 10^?6 ns^?1 with signal-to-noise ratio 27 dB at the optimum operation point of this detector. The designed single-photon detector achieves a tradeoff between lower dark count rates and high quantum efficiency.     

Time-resolved diffuse optical spectroscopy up to 1700 nm by means of a time-gated InGaAs/InP single-photon avalanche diode

We present a new compact system for time-domain diffuse optical spectroscopy of highly scattering media operating in the wavelength range from 1100 nm to 1700 nm. So far, this technique has been exploited mostly up to 1100 nm: we extended the spectral range by means of a pulsed supercontinuum light source at a high repetition rate, a prism to spectrally disperse the radiation, and a time-gated InGaAs/InP single-photon avalanche diode working up to 1700 nm. A time-correlated single-photon counting board was used as processing electronics. The system is characterized by linear behavior up to absorption values of about 3.4 cm(-1) where the relative error is 17%. A first measurement performed on lipids is presented: the absorption spectrum shows three major peaks at 1200 nm, 1400 nm, and 1700 nm.     

A model for diffusion of beryllium in InGaAs/InP heterostructures

This study reports on Be diffusion from a Be-doped (3×10¹⁹ cm⁻³) In_0.53Ga_0.47As layer sandwiched between undoped InP layers grown by gas source molecular beam epitaxy. To explain the obtained experimental depth profiles, a kick-out model of substitutional interstitial diffusion mechanism, involving neutral Be interstitials for the InGaAs epilayer and singly positively charged Be interstitials for the InP epilayers, is proposed. Using the boundary conditions at the heterojunctions and taking into account the built-in electric field, Fermi level and bulk self-interstitial generation/annihilation effects, we obtained a good agreement between the simulated and experimental data.     

基于InP衬底的应变和应变补偿的InGaAs／InAlAs材料的高分辨X射线衍射分析

高分辨率X射线衍射技术被用来分析基于InP衬底的应变的InGaAs和InAlAs单层材料和应变补偿的InGaAs/InAlAs超晶格材料.通过倒空间mapping得到的单层材料的错向角大约为10-3度,可以忽略不计.通过摇摆曲线得到了单层材料的组分和体失配度,接着单层材料的结果被用来分析在相同的条件下利用MBE技术生长的超晶格材料.利用倒空间mapping精确得到了超晶格的平均垂直失配度和各层的厚度,通过X射线模拟软件得到的超晶格材料的模拟曲线和实测曲线吻合的很好.     

A TEM and SEM-cathodoluminescence study of oval defects in graded InGaAs/GaAs buffer layers

The nature of oval defects in compositionally graded InGaAs/GaAs buffer layers has been investigated by means of Transmission electron microscopy (TEM) and Cathodoluminescence (CL). CL spectra show that emissions from within the defects have energies lower than that from the defect-free regions, thus demonstrating that the defects are richer in In than the surrounding matrix. No In particles have been detected within the defect core. TEM investigations reveal that the defects form in the topmost strained regions close to the surface and originate from stacking faults.     

10×10InGaAsP/InP阵列波导光栅器件的研制

研制了脊形波导结构的10×10InGaAsP/InP阵列波导光栅器件(AWG),并采用掺铒光纤放大器(EDFA)作宽带光源测量了AWG的近场图以及分光特性。     

Interface control of InGaAs/AlAsSb heterostructures

We report here a photoluminescence (PL) study of AlAsSb/InGaAs/AlAsSb single quantum wells (SQWs) that are lattice-matched to InP substrates grown by molecular beam epitaxy (MBE). The group V species used, the interface termination procedures, and Si doping are shown to markedly influence the PL spectra of the SQWs: (1) the undoped SQWs grown using dimer group V species combined with As interface termination show sharp PL spectra, which correspond to a direct transition between the confined electrons and holes of InGaAs; (2) the PL peak is broadened and shifted towards a longer wavelength as a result of Sb interface termination; and (3) when the AlAsSb or InGaAs layers are highly doped to 1×10¹⁹ cm⁻³, the PL spectra become very broad. These results are most probably attributable to the enhanced exchange reaction between As and Sb, and also to the diffusion of In and Ga at the interfaces resulting from Si high doping and the use of tetramer group V species.     

Ag/InP复合材料的制备、表征及其性能

通过溶剂热法制得磷化铟微晶,然后以光化学还原法成功将Ag单质均匀地复合到磷化铟微晶表面,制备Ag/InP复合材料。采用X射线衍射仪和扫描电子显微镜等对所得产物进行分析,结果表明:复合材料由尺寸为500nm左右的球状微晶组成,其中20nm左右的Ag纳米颗粒均匀附着在立方相InP微球表面上,表面较为粗糙。以刚果红为目标降解物,利用荧光和紫外光谱对所得产物进行光催化性能测试,结果发现,与单体InP微晶相比,Ag/InP复合材料形成后,其对刚果红的光催化降解活性提高,这可能是由于Ag纳米颗粒均匀附着后,有效分离InP的光生电子和空穴。此外,对不同银负载量的Ag/InP的光催化性能进行研究。研究表明:当负载量为73.3%时,所得产物的光催化性能最佳,降解率可达64%。     

Temperature dependent study on the microwave noise performance of metamorphic InP/InGaAs heterojunction bipolar transistors

In this study, a detailed characterization on the microwave noise performance of high gain metamorphic heterojunction bipolar transistor (MHBT) in the temperature range of 300 K to 380 K is performed. The results are compared between the MHBT and the referenced lattice-matched InP HBT (LHBT) devices. The minimum noise figure (NF_min) versus frequency in the range of 2 to 20 GHz at different temperatures for a 1.6 × 20 μm² HBTs are measured. The experimental results show that the MHBT exhibits a slightly larger variation in NF_min compared to lattice-matched HBTs. Even though the MHBTs may have much higher thermal resistance, this may not significantly affect the device microwave noise performance.     

Influence of LPE growth conditions on the electroluminescence properties of InP/InGaAs(P) infrared emitting diodes

Liquid phase epitaxial growth of InP/InGaAs(P) infrared emitting diodes was studied systematically. Small area surface emitting LED chips were prepared to cover completely the 1100–1700 nm wavelength ranges. Nine different diodes were fabricated with optimal spacing of the peak emission wavelengths in order to have sufficient overlapping of their spectra. Efficient LEDs with narrow spectra have been realised by careful selection of the layer structure and growth conditions. Thick active layers with constant composition and abrupt interfaces have been grown for each emission wavelength. The long wavelength diodes (1275–1675 nm) were grown with additional quaternary layer(s) to prevent the melt-back of the active layer by InP melt. Low growth temperature (590°C) was used to prepare the LED structures. In the spectral range of 1250–1520 nm higher growth temperatures (625–645°C) were necessary to improve the device parameters. Such phenomena confirm the existence of the miscibility gap in the InGaAsP quaternary crystal system. Quaternary layers grown in the middle of the immiscibile region showed non-uniform composition and ragged interfaces at the upper heterojunction.     

自组织InAs/GaAs与InGaAs/GaAs量子点生长及退火情况的比较

本文采用MBE进行InAs/GaAs与InGaAs/GaAs量子点的生长,利用RHEED进行实时监测,并利用RHEED强度振荡测量生长速率。对生长的InAs/GaAs和InGaAs/GaAs两种量子点生长过程与退火情况进行对比,观察到当RHEED衍射图像由条纹状变为网格斑点时,InAs所需要的时间远小于InGaAs;高温退火下RHEED衍射图像恢复到条纹状所需要的时间InAs比InGaAs要长。