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.
The nanopore-structure YBa2Cu3O7 (YBCO) high-temperature superconducting detectors are novel with their possible phase transition mechanism from insulating to metallic states. In this paper, an array of YBCO nanopore detectors were fabricated and evaluated. Very thin YBCO films were deposited on strontium titanate substrates, and 16×1 high-temperature superconducting detectors were prepared by photolithography, etching and evaporation processes. Connected with the specially designed and developed readout circuit, the detectors were tested in terms of resistance-temperature (R-T) and voltage-current (I-V) characteristics. The R-T curve confirms the insulating phase of the nanopore superconducting YBCO film at low temperature. With increasing the incident intensity of 1550nm light, the resistance of the detector reduces significantly, implying the photoinduced metallic-conduction phase. The photoresponse is detectible under 1550 nm irradiation down to ~10nW, suggesting the possibility of highly sensitive photodetection. Our new devices may have application prospects in many fields such as quantum communication and aerospace detection.
Wideband detectors are becoming more and more widely used. In order to expand the response wavelength of silicon detectors, single-layer and double-layer antireflection coatings are used, and combined with the high gain characteristics of silicon avalanche photodetectors (APDs), their response band is extended to the range of 250-1100nm. Simulation analysis shows that the double layer antireflection coating has larger infrared enhancement than the single layer anti reflection coating. The Si APD with this structure can achieve high response from UV 250nm to 1100nm with multiplication, enabling efficient detection in the UV-visible-near-infrared band.
The simulations of quasi one-dimensional (1D) and quasi three-dimensional (3D) device process and optoelectronic performance were conducted on silicon APD array pixels using Silvaco, realizing micro region analysis of the electric field distribution, avalanche gain, and photoelectric response characteristics of the APD photosensitive region. The multiplication coefficients corresponding to different positions of APD pixel were obtained and compared with the ideal 1D device structure. The results show that the multiplication factor of the center region of APD pixel is significantly higher than that of the edge of the photosensitive region. The simulation of microlens to converge the incident light to the center of the photosensitive region confirmed the increasement of APD avalanche multiplication current, i.e. the quasi 3D structural APD response is increased from 13.6 A/W to 54.8 A/W, and the effective fill factor is increased from 20.9% to 84.2%. Thus, the utilization rate of incident light is effectively improved.
Negative feedback avalanche diode (NFAD) has the advantages of fast quenching speed, low afterpulsing and easy integration. It can be used in quantum communication, fluorescence spectrum detection, single-photon counting imaging and other applications. The research on NFAD devices and their application in single-photon detecting system has thus been of great significance. This paper describes the novel design of NFAD, and reviews the development and application of NFAD devices in recent years. By monolithically integrating a film resistance onto single photon avalanche diode (SPAD), the formed self-passive quenching circuit in NFAD brings about improvements in especially afterpulsing, and effectively enables photon number resolution. Further hybridizing active quenching circuit, the single-photon detection system composed of NFAD performs much better than that of conventional SPAD. NFAD demonstrates more practical application potential so that it will be much more powerfully developed in the future, as we prospect finally in this paper.
This paper summarizes the research progress of SiGe preparation technology at home and abroad, summarizes the advantages and disadvantages of low-voltage silicon epitaxy and molecular beam epitaxy, and discusses the applications of SiGe Heterojunction materials in pin, APD and waveguide laser detectors. Based on the development of black silicon preparation technology at home and abroad, femtosecond laser, wet etching and dry etching are discussed, and their applications in laser detectors are reviewed. Finally, the development prospects of the two materials and their application prospects are summarized and prospected, and the follow-up development direction is given.
In this paper, we simulated and analyzed the effects of guard-ring’s depth and space on the performance of silicon avalanche photodetector (APD) based on the traditional n+-p-π-p+ structure. Two shallow trenches (ST) outside of the active region was used as the guard rings and the effects of depth and the spacing between the two ST on the performance of silicon APD arrays was simulated and analyzed. In order to optimize the parameters of the shallow trenches, we calculated the different characteristics of APD under different conditions, including the characteristics of APD such as breakdown voltage, multiplication factor, dark current, photocurrent and so on. The result shows the breakdown voltage and multiplication of APD become higher because of the shallow trench guard-rings and they are related to the PN junction depth.
The self propagating welding of Kovar and sapphire was carried out with NiAl nano multilayers. The samples were tested by X-ray machine, scanning acoustic microscope, scanning electron microscope and bonding tester. The results show that sapphire and Kovar can be well self propagating welded using multilayer NiAl nano multilayers as heat source and solder to form uniform weld joint. The void ratio of the weld joint is 1.1%, and the welding strength is ~ 3.38 MPa. This study lends credible the welding of sapphire and similar metal materials.
Transmission properties of transverse magnetic light through periodic sub-wavelength slit apertures on a metallic film, behind which is another planar metallic film, are studied by finite-difference-time-domain method with constant periodicity and slit width. The result shows that the transmitted energy is strongly correlated to both the thickness of the metallic grating and the distance between such two films at a specific wavelength. The thickness of the grating acts as a filter that allows specific wavelengths to go through the slits, while the distance of dual metallic film dominantly determines a constructive or destructive interference between the transmitted light through the slits and the reflected wave from the back film. Besides, a strong vibration in the transmission spectrum as a function of the grating thickness is interestingly observed, which can be interpreted by the resonance of the surface plasmons of the front and the back metallic films.
Impact ionization in charge layer and multiplication layer of InAlAs/InGaAs avalanche photodiodes (APDs) with separated absorption, grading, charge and multiplication structures has been studied by two-dimensional simulations using Silvaco TCAD. Special attention has been paid to the charge layer and multiplication layer with different thicknesses and doping concentrations in order to optimize the structure for low band discontinuities and an appropriate electric field distribution. Band-edge profile calculations as well as current–voltage characteristic and electric field results of the APDs will be discussed in this article.
A hybrid integrated photodetector consisting of array of reach-through avalanche photodiodes and readout integrated circuit chips was developed. The reach-through avalanche photodiode model with separate layer of absorption, charge and multiplication are elaborated. This kind of photodiode is optimized for detection of 905 nm radiation and in that range achieve excellent parameters – high gain, low noise and high speed. Next, the design and properties of the readout integrated circuit with a new-type regulated cascode circuit configuration are discussed. The linear array reach-through avalanche photodiode and readout integrated circuit chips were integrated into a photodetector by using bonder-leading welding techniques. The integrated detector demonstrates the pulse responsivity R ≥ 1×106 V/W, the noise equivalent power NEP ≤ 5 pW/Hz1/2, and the rise time tr ≤ 3 ns, under pulsed laser irradiation at 905 nm, 100 ns and 10 KHz.
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