This article reports a multi-gain-stage avalanche photodiode based on InGaAs/InAlAs superlattice, which has much higher gain and signal-to-noise ratio than conventional APD. The physical mechanism of high gain and low noise of this type of APD is analyzed in detail, and the dead space gain theory (DSMT) is introduced and applied to the calculation of the excess noise factor of multi-gain-stage APD. For a 5-stage device, the distribution of electric field and carrier dead space is calculated, and the ionization rates before and after considering phonon scattering are compared. The gain vs excess noise factor curve is obtained and compared with the traditional McIntyre model. The simulation results shows that the excess noise factor is equivalent to the McIntyre model k=0.049. Based on the simulation results, an optimized epitaxial material structure is designed, Front-illuminated photo diode were etched in the molecular beam epitaxy (MBE)-grown epitaxial material, the mesa sidewalls were encapsulated with Si3N4 . The test results of a 50μm diameter device are as follows: maximum above 1000, excess noise factor of 2.39@M=100, spectral response range of 0.95~1.65μm, response time of 1.26ns.
In this paper, the research and analysis of mesa-type InGaAs FPA detectors with various pixel structures were reported. Three different pixel mesa structures in FPA were designed, including conventional mesa structure, double-mesa and surface pn junction mesa. The numerical simulation of above three pixel mesa structure devices and the conventional pixel planar structure device was carried out, and the optimal pixel structure was determined by comparing the electrical crosstalk and dark current. The results showed that the surface pn junction mesa structure can reduce the surface leakage current of the device by effectively suppressing the electric field of the device mesa etched surface, which was beneficial for reducing the difficulty of passivation protection process. InGaAs FPA detectors with surface pn junction mesa structure can simultaneously have relatively low electrical crosstalk and low dark current characteristics.
Using the frequency domain analysis method, the thermocouple time constant in the dynamic measurement of laser power is analyzed, and the pole of the thermocouple is compensated by the frequency domain analysis method, thus expanding the frequency domain range of the measurement system. On this basis, by measuring the response curve of the power detector, its time constant is determined, and its transfer function is obtained by designing a predictive circuit. The designed prediction circuit is simulated, and the optimal design parameters are obtained, which doubles the frequency response and reduces the response time constant to the step function from T to T/2. Through the test of the actual circuit, the results are basically consistent with the theoretical calculation results, which can meet the rapid detection needs of high-power detectors.
InGaAs-based p-i-n Photo-Detectors (PDs) on misoriented Si and conventional Si substrates are both designed, fabricated, and characterized. It is found that the as-grown PD structure on misoriented Si substrate has lower dislocation density than on conventional Si substrate. The PD fabricated on misoriented Si substrate shows a low dark-current of 83nA under −5 V, a zero bias voltage responsivity of 0.58 A/W at 1550 nm, the corresponding quantum efficiency is 46%. The dark-current and quantum efficiency at 1550 nm, of the PD on misoriented Si substrate, is about over one orders of magnitude lower and 70% higher respectively, than the comparison PD fabricated on conventional Si substrate.
InGaAs/InP Negative Feedback Avalanche Diode (NFAD), with a quenching negative feedback resistor integrated, is a new type of high-sensitivity and all-solid-state semiconductor device based on Single Photon Avalanche Diode (SPAD) structure. This paper proposes a near-infrared free-running single photon counting integrated module based on InGaAs/InP NFAD. It contains an active quench and extraction circuit, sampling and processing circuit, upper computer software design and TEC etc., and is designed to serve a NFAD adopting absorption-attenuation-charge-multiplication (SAGCM) structure with InGaAs/InP materials and operating in Geiger mode. In this module, we specifically design a full differential amplifier and comparator to exploit the performance of NFAD by detecting and extracting the weak avalanche signal and converting it into TTL pulse. The avalanche detection discrimination threshold voltage is adjustable by external high-precision DAC, and a programmable dead time could be set by Field Programmable Gate Array (FPGA). The module system provides timing logic in order to avoid false counting caused by the coupling noise of the differential amplifier. By developing Graphical User Interface (GUI) program, we are able to setup detector working parameters configuration, to display real-time counting data and to further meet different application requirements. The fabricated module exhibits good NFAD performance with PDE of 7.9% and 15.8%, DCR of 1.37 kHz and 1.06 kHz and the after-pulse probability of 34.2% and 16.8% at 223 K, 1550 nm with dead time of 200 ns and 1 μs, respectively. It turns out that a near-infrared single photon counting system possessing fast detection speed, fast quenching time, flexible dead time adjustment, small size and high integration will be available in the near future to strongly support lidar and quantum information facilities.
Single photon flash light detection and ranging (LiDAR), which is based on Geiger Mode avalanche photodiode (GMAPD) array, enables superior sensitivity and detection range to obtaining depth information. The Flash LiDAR captures an entire 3D image by single laser pulse, much faster than conventional LiDAR based on the scanning of a single detector over the scene. In conventional advanced driver assistant systems (ADAS), closer and weaker reflections caused by the environmental factors will cause misidentification. Furthermore, power dissipation and limited pixel size are enormous challenges for Readout Integrated Circuit (ROIC) design. The paper proposes the design of ROIC with Multi-Echo Detection for 128×32 GM-APD Array. The pixel includes active quenching and reset circuit of GM-APD, and embedded 11-bit Time to Digital Converter (TDC) offers precise distance resolution by Time of Flight (TOF) measurement. The proposed ROIC is designed with 0.18μm CMOS process. Due to shared DFFs by TDC and shift register, 90μm pixel pitch is realized with Multi-Echo Detection function. Global clock gating(GCG) and shift clock gating(SCG) techniques bring the power dissipation down to 464.6mW.
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