Conventional Avalanche Photodiodes Research Articles

108 m Underwater Wireless Optical Communication Using a 490 nm Blue VECSEL and an AOM.

Advanced light sources in the blue-green band are crucial for underwater wireless optical communication (UWOC) systems. Vertical-external-cavity surface-emitting lasers (VECSELs) can produce high output power and good beam quality, making them suitable for UWOC. This paper presents a 108 m distance UWOC based on a 100 mW 490 nm blue VECSEL and an acousto-optic modulator (AOM). The high-quality beam, which is near diffraction-limited, undergoes relatively small optical attenuation when using a conventional avalanche photodiode (APD) as the detector and employing 64-pulse position modulation (PPM). At the time-slot frequency of 50 MHz, the bit error rate (BER) of the UWOC was 2.7 × 10-5. This is the first reported AOM-based UWOC system with a transmission distance over 100 m. The estimated maximum transmission distance may be improved to about 180 m by fully utilizing the detection accuracy of the APD according to the measured attenuation coefficient of the blue VECSEL used. This type of UWOC system, composed of a high-beam-quality light source and a conventional detector, make it more closely suited to practical applications.

Demonstration of the AlInAsSb cascaded multiplier avalanche photodiode

By utilizing the low-noise benefits of staircase avalanche photodiodes (APDs) and the high-field tolerance of conventional APDs, a “cascaded multiplier” device has been grown and characterized showing significantly reduced excess noise compared to k ∼ 0 materials. Because it can withstand higher electric fields than a pure staircase APD, the gain values are not limited by the number of staircase steps in the device, and higher gains are demonstrated. In addition, the cascaded multiplier device shows reduced dark current to staircase devices of similar gain. Slight adjustments to the device design could increase the gain to even higher values—further improving the signal-to-noise ratio in the detector.

Resonant InGaAs Detectors and Emitters for Passive and Active Imaging Application

In this work, we design an InGaAs avalanche photodiode (APD) with a higher photocurrent to dark current ratio than a conventional APD. The improvement is based on optical confinement in an optical resonator, which increases the optical intensity in the detector volume and thus its quantum efficiency. With optical confinement, the absorbing layer can be 20 times thinner than the conventional APD, reducing the intrinsic generation-recombination dark current by the same amount and still be able to produce 90.9% of the photocurrent. The photocurrent to intrinsic dark current ratio can thus be increased theoretically by 18.2 times in concomitant with a lower operating voltage. Higher photocurrent can also be obtained using a thicker absorber. Besides APDs, the optical resonator structure can also be applied to p-i-n photodiodes for similar improvement. To further increase the detection sensitivity, we design an efficient InGaAsP light emitting diode (LED) having a similar resonator geometry. The resonator geometry enables more collimated emission and increases the optical power theoretically by more than 36 times compared to a conventional LED. Integrating the resonant APD and LED together will yield a powerful SWIR transceiver for various low light, LIDAR, and 3-dimensional imaging applications.

Performance comparisons between inverted and conventional avalanche photodiodes for larger capacity applications

Performance comparisons between inverted and conventional avalanche photodiodes for larger capacity applications

A Complete Two-Dimensional Avalanche Photodiode Based on MoTe2−WS2−MoTe2 Heterojunctions With Ultralow Dark Current

Two-dimensional (2D)-material-based photodetectors have recently received great attention due to their potentials in developing ultrathin and highly compact devices. Avalanche photodiodes (APDs) are widely used in a variety of fields such as optical communications and bioimaging due to their fast responses and high sensitivities. However, conventional APDs based on bulk materials are limited by their relatively high dark current. One solution to tackle this issue is by employing nanomaterials and nanostructures as the active layers for APDs. In this study, we proposed and fabricated an atomically-thick APD based on heterojunctions formed by 2D transition metal dichalcogenides (TMDs). A typical device structure was formed by stacking a semiconducting monolayer WS2 onto two metallic few-layer MoTe2 flakes. Due to the Schottky barrier formed between the TMD layers and their atomic thicknesses, the dark current of the APD is greatly reduced down to 93 pA. In addition, the APD can operate through a broad spectral range from visible to near-infrared region, with a responsivity of 6.02 A/W, an external quantum efficiency of 1,406%, and an avalanche gain of 587. We believe that the 2D APD demonstrated here provides a feasible approach for developing all-2D optoelectronic devices with simultaneous high-sensitivity and low noise.

AlGaN solar-blind ultraviolet avalanche photodiodes with a p-graded AlxGa1-xN layer and high/low Al-content AlGaN multiplication layer

We design a back-illuminated p–i–n–i–n separate absorption and multiplication (SAM) AlGaN solar-blind avalanche photodiode (APD) with a low Al-content p-graded AlxGa1-xN layer and a high/low Al-content AlGaN multiplication layer. Simultaneously, an III-nitride AlN/Al0.64Ga0.36 N distributed Bragg reflector (DBR) structure is inserted to improve the solar-blind photoresponse for the designed APD. The simulation results show that the designed APD exhibits enhanced optoelectronic characteristics compared to the conventional APD, which is attributed to the higher holes impact ionization coefficient and generated polarization electric field in the same direction as the applied bias field of the designed APD. The designed APD exhibits significant enhanced avalanche gain and reduced avalanche breakdown voltage compared with the conventional APD.

Niobium nitride plasmonic perfect absorbers for tunable infrared superconducting nanowire photodetection.

Quantum technologies such as quantum computing and quantum cryptography exhibit rapid progress. This requires the provision of high-quality photodetectors and the ability to efficiently detect single photons. Hence, conventional avalanche photodiodes for single photon detection are not the first choice anymore. A better alternative are superconducting nanowire single photon detectors, which use the superconducting to normal conductance phase transition. One big challenge is to reduce the product between recovery time and detection efficiency. To address this problem, we enhance the absorption using resonant plasmonic perfect absorber effects, to reach near-100% absorption over small areas. This is aided by the high resonant absorption cross section and the angle insensitivity of plasmonic resonances. In this work we present a superconducting niobium nitride plasmonic perfect absorber structure and use its tunable plasmonic resonance to create a polarization dependent photodetector with near-100% absorption efficiency in the infrared spectral range. Further we fabricated a detector and investigated its response to an external light source. We also demonstrate the resonant plasmonic behavior which manifests itself through a polarization dependence detector response.

Experimental observation of the linear gain of back-illuminated ultraviolet avalanche photodiodes using a GaN/AlN periodically stacked structure

Semiconductor-based avalanche photodiodes (APDs) have the advantages of lower power and simpler fabrication of arrays compared with photomultiplier tubes. It is critical for weak-light imaging that the APD is operated under back illumination and with high linear gain. However, linear gain is fairly low for conventional PIN APDs. This paper presents a back-illuminated APD, whose multiplication layer is designed to be a GaN/AlN periodically stacked structure. The GaN/AlN heterostructure is introduced to enhance the ratio of ionization coefficient between electrons and holes, which proves to be helpful for increasing the linear gain. Under back illumination, the prototype device demonstrates a record-high external quantum efficiency (reflecting linear gain) of ∼5 × 102 at the reverse bias of 66 V. The device response spectra were also studied to further confirm that only the photo-excited electrons can trigger the collision ionization in the multiplication layer.

Design of a bandgap-engineered barrier-blocking HOT HgCdTe long-wavelength infrared avalanche photodiode.

The performance of high-operating-temperature (HOT) longwavelength infrared (LWIR) HgCdTe avalanche photodiodes (APDs) is significantly limited by the increasing dark current related to temperature. In this paper, a novel barrier-blocking LWIR pBp-APD structure is proposed and studied, and the results show that the dark current of pBp-APD is significantly restricted compared with conventional APD without sacrificing the gain at high temperature. Furthermore, the reduction of avalanche dark current is found to be the key points of the significant suppression of dark current. The physical essence of this reduction is revealed to be the depletion of carriers in the absorption region, and the feasibility of the improved structure is further confirmed by the analysis of its energy band and electric field distribution. In addition, the reduction of gain-normalized dark current (GNDC) does not need to sacrifice the gain. The proposed LWIR pBp-APD paves the way for development of high operation temperature infrared APDs.

Optoelectronic properties of multiple quantum barriers nano-scale avalanche photo diodes

The important optoelectronic properties like spectral response, excess noise characteristics, time and frequency response of multiple quantum barrier (MQB) nano-scale avalanche photodiodes (APDs) based on Si~3C-SiC material system have been studied. A self-consistent simulation method based on quantum drift-diffusion model has been presented. Simulation results show that the Si~3C-SiC MQB nano-APDs are capable of detecting significantly longer wavelengths as compared to infrared flat Si APDs. The multiplication gain and excess noise factor (ENF) of the MQB APDs have been calculated by varying the number of quantum barriers (QBs). The numerically calculated ENF values of MQB APDs have been compared with the ENF of Si flat conventional APDs of similar dimensions and it is observed that the use of QBs leads to significant reduction in ENF of the APDs. Simulation results also show that MQB nano-APDs possess significantly faster time response and wider frequency response as compared to the Si counterparts.

Utilizing niobium plasmonic perfect absorbers for tunable near- and mid-IR photodetection.

With the fast development of single photon-based technologies such as quantum computing and quantum cryptography, conventional avalanche photodiodes as single photon detectors are not the optimum tools anymore. They are currently replaced by Superconducting Nanowire Single Photon Detectors (SNSPDs) based on the superconducting to normal conducting phase transition. The current challenge with SNSPDs lies in overcoming the trade-off between detection efficiency and recovery time. While a large active area will lead to high detection efficiency, the associated high kinetic inductance causes a long recovery time. Plasmonic effects can play an important role in the absorption enhancement of SNSPDs. Nanostructuring with a suitable geometry can provide a high-absorption cross-section at the intrinsic nanowire surface plasmon resonance, which can be significantly larger than their geometric cross-section. We present a photodetector based on the intrinsic localized surface plasmon resonance of a niobium nanowire, which is one of the common superconductors with low kinetic inductance. Additionally, we are increasing the absorption of our nanostructures even further using a plasmonic perfect absorber scheme. We fabricated a plasmonic perfect absorber superconducting photodetector, investigated its response to external light at resonance, and proved its plasmonic behavior as evidenced by its polarization dependence.

AlGaN Solar-Blind Avalanche Photodiodes With p-Type Hexagonal Boron Nitride

To improve the performances of AlGaN solar-blind avalanche photodiodes (APDs), we propose a separate absorption and multiplication AlGaN APD with a p-hBN layer. The simulated results show that the p-hBN/AlGaN APD significantly decreases the breakdown voltage almost by 23% in comparison with the conventional AlGaN APD due to the use of p-hBN, which has a wider bandgap, a higher p-type doping efficiency, and a smaller spontaneous polarization. Moreover, the designed APD keeps an intrinsic solar-blind characteristic even at large reverse bias because the h-BN is completely transparent in the long wavelength direction outside the solar-blind region. The result also confirms that the p-hBN/AlGaN APD has the lower Flicker and impact ionization noise at low and medium frequency under breakdown voltage.

Modeling a novel InP/InGaAs avalanche photodiode structure: Reducing the excess noise factor

Abstract We proposed one structure of InP/In 0.53 Ga 0.47 As avalanche photodiode (APD) with a multi-layer multiplication which is created by inserting a p-type layer into a conventional lightly doped multiplication region. It is shown that the performance of the excess noise factor F is improved compared to the conventional APD structure. A carrier multiplication model, incorporating the dead space effect, is demonstrated. Moreover, we used the model with generation–recombination process and surface leakage current to calculate the excess noise factor F of the multi-layer multiplication APD and conventional APD structure, respectively.

A High-Linearity Avalanche Photodiodes With a Dual-Carrier Injection Structure

This letter presents a novel avalanche photodiode (APD) featuring a unique absorber that provides high-linearity operation. Different from conventional APDs, this APD has an absorber at both sides of the avalanche layer. This configuration effectively suppresses hole accumulation and the space-charge effect in the absorber. The fabricated APD exhibits an improved 1-dB compression point corresponding to an input power of −6.3 dBm at a gain of 10. It was found that its excess-noise characteristics are comparable to those of conventional electron-injection type and InAlAs APDs even though the new APD operates according to a dual-carrier injection and multiplication principle.

Fine Control of the Electric Field Distribution in the Heterostructure Multiplication Region of AlGaN Avalanche Photodiodes

To enhance avalanche ionization, we designed a new separate absorption and multiplication AlGaN solar-blind avalanche photodiode (APD) by replacing the conventional AlGaN homogeneous multiplication region with a high/low Al content AlGaN heterostructure layer. The calculated results showed that the improved APD with the Al0.3 Ga0.7N/Al0.45Ga0.55N heterogeneous multiplication region exhibits 51% higher gain than that of the conventional APD, benefiting from the six times higher hole ionization coefficient of Al 0.3Ga0.7N, compared to that of Al0.45Ga0.55N. Furthermore, we inserted an intermediate n-type AlGaN charge layer into the heterogeneous multiplication region to obtain superior performance by finely controlling the electric field distribution. The dependence of breakdown voltage and multiplication gain on the Al content, doping concentration, and thickness of the charge layer is studied in detail to get the optimal structure. Meanwhile, the solar-blind characteristic is also taken into account when optimizing the APD structure.

AlGaN solar-blind APD with low breakdown voltage

A p-i-i-n type AlGaN heterostructure avalanche photodiodes (APDs) is proposed to decrease the avalanche breakdown voltage and to realize higher gain by using high-Al-content AlGaN layer as multiplication layer and low-Al-content AlGaN layer as absorption layer. The calculated results show that the designed APD can signifi-cantly reduce the breakdown voltage by almost 30%, and about sevenfold increase of maximum gain compared to the conventional AlGaN APD. The noise in designed APD is also less than that in conventional APD due to its low dark current at the breakdown voltage point. Moreover, the one-dimensional (1D) dual-periodic photonic crystal (PC) with anti-reflection coating filter is designed to achieve the solar-blind characteristic and cutoff wavelength of 282 nm is obtained.

An improved design for AlGaN solar-blind avalanche photodiodes with enhanced avalanche ionization**Project supported by the State Key Project of Research and Development Plan, China (Grant No. 2016YFB0400903), the National Natural Science Foundation of China (Grant Nos. 61634002, 61274075, and 61474060), the Key Project of Jiangsu Province, China (Grant No. BE2016174), the Anhui University Natural Science Research Project, China (Grant No.

To enhance the avalanche ionization, we designed a new separate absorption and multiplication AlGaN solar-blind avalanche photodiode (APD) by using a high/low-Al-content AlGaN heterostructure as the multiplication region instead of the conventional AlGaN homogeneous layer. The calculated results show that the designed APD with Al0.3Ga0.7N/Al0.45Ga0.55N heterostructure multiplication region exhibits a 60% higher gain than the conventional APD and a smaller avalanche breakdown voltage due to the use of the low-Al-content Al0.3Ga0.7N which has about a six times higher hole ionization coefficient than the high-Al-content Al0.45Ga0.55N. Meanwhile, the designed APD still remains a good solar-blind characteristic by introducing a quarter-wave AlGaN/AlN distributed Bragg reflectors structure at the bottom of the device.

High performance silicon carbide avalanche‐p‐i‐n ultraviolet photodiode with dual operation models

Silicon carbide-based quasi-separated-absorption-multiplication ultraviolet avalanche photodiode (APD) with a small-area multiplication region and a large-area absorption region, which comprises of a p+nn− junction encircled by a p+n− junction, is proposed, and its optoelectronic performance is modelled. The modelling results show a 4H-SiC APD with high performance can be achieved. Moreover, when operated at a low reverse bias (e.g. 5.0 V), the photodiode has almost the same optoelectronic characteristics as the 4H-SiC p-i-n photodiode. It is noted that the device has benefited advantages of both conventional separate absorption and multiplication APD and p-i-n photodiode in the wavelength range of ultraviolet detection, which enable the dual operation models of the device.

Al0.4Ga0.6N/Al0.15Ga0.85N Separate Absorption and Multiplication Solar-Blind Avalanche Photodiodes With a One-Dimensional Photonic Crystal Filter

An Al 0.15Ga 0.85N/Al 0.4Ga 0.6N separate absorption and multiplication avalanche photodiode (APD) integrated with the 1-D photonic crystal (PC) filter with a three-period antireflection coating between the air and periodic PC units on the back of the sapphire substrate are designed and studied. The calculated results show that the designed Al 0.15Ga 0.85N/Al 0.4Ga 0.6N APD has a much higher gain and a steeper spectral responsivity cutoff edge in the solar-blind region, and its peak responsivity and ultraviolet/visible rejection ratio are enhanced near 110% and 230%, respectively, when compared with the conventional AlGaN APD. Moreover, the antireflection coatings used in the designed APD can obviously improve the spectral response curve and the spectral responsivity due to its significant suppression to the reflectivity the in solar-blind region.

Energy Resolution Contributions in Reach-Through Avalanche Photodiodes

Avalanche photodiodes (APD) are used in the muonic helium Lamb shift experiment for detection of 8 keV X-rays. Reach-through APDs from Hamamatsu Photonics have been investigated for X-ray detection as alternative to conventional APDs. In order to evaluate the different contributions to the energy resolution obtained in a reach-through APD, its response to both 8 keV X-rays and visible light pulses was investigated. The intrinsic resolution was estimated by further measurements of the electronic noise contribution and the gain non-uniformity was assessed. The excess noise factor was determined. Results at different temperatures are presented.