PIN Photodetector Research Articles

Si/Ge/Si Photodetector by Rapid-Melting-Growth Technique

For high-speed data processing, the synergy of photons and electrons requires their absorption and conversion characteristics to be suited for near-infrared optical communication. Here, we report on the formation of high-quality germanium on oxide for photodetectors as well as its characteristic measurements. The Ge film was made by using the rapid-melting-growth technique, and the quality was verified by Raman spectroscopy and standard electron microscopy. The high-quality Ge was integrated with P-type and N-type silicon pillars to form a PIN photodetector. The electrical measurement identified its responsivity to the near-infrared spectrum. This work demonstrated that a high-quality Ge film can be obtained using a metal-oxide-semiconductor field-effect transistor compatible process with good photoelectric conversion efficiency and responsivity.

A versatile digitally-graded buffer structure for metamorphic device applications

Exploring more effective buffer schemes for mitigating dislocation deficiencies is the key technology towards higher performance metamorphic devices. Here we demonstrate a versatile metamorphic grading structure consisting of 38-period alternated multilayers of In0.52Al0.48As and In0.82Al0.18As on InP substrate, thicknesses of which in each period were gradually varied in opposite directions from 48.7 and 1.3 nm to 1.3 and 48.7 nm, respectively, akin to a digital alloy. Both preferentially dislocation nucleation and blocking of threading dislocation transmission are observed near the In0.82Al0.18As/In0.52Al0.48As interfaces, which help relax the strain and lower the residual defect density. A 2.6 μm In0.83Ga0.17As pin photodetector is fabricated on this pseudo-substrate, attaining a low dark current density of 2.9 × 10−6 A cm−2 and a high detectivity of 1.8 × 1010 cmHz1/2W−1 at room temperature, comparable with the states of the art that on linearly-graded buffer layers. These results indicate such digitally-graded buffer structures are promising for enhancing performances of metamorphic devices, and can be easily generalized to other lattice-mismatched material systems.

In0.83Ga0.17As photodetectors with different doping concentrations in the absorption layers

The performances of wavelength-extended In0.83Ga0.17As PIN photodetectors with 8 × 1015 or 4 × 1016 cm−3 doped absorption layers were investigated and compared at different temperatures and bias voltages. Results displayed that they showed comparable device performance around room temperature and low bias voltages, but relatively large difference at lower temperatures and higher bias voltages. At lower operation temperatures the In0.83Ga0.17As photodetectors with 8 × 1015 cm−3 doped absorption layers showed smaller dark currents and higher resistance area products R0A than those with 4 × 1016 cm−3 doped absorption layers. It was ascribed to the reduced trap-assisted tunneling dark current in the photodetector with the lower doped In0.83Ga0.17As absorber layer.

Performance evaluation of InAs/GaSb superlattice photodetector grown on GaAs substrate using AlSb interfacial misfit array

We report on the growth and opto-electronic characterization of type-II InAs/GaSb superlattice (SL) mid-wavelength infrared pin photodetector grown on a GaAs substrate. AlSb interfacial misfit array was employed at the GaAs buffer/GaSb epilayer interface to reduce the dislocation density of the SL structure grown on the lattice mismatched GaAs substrate. Optical and electrical performance of this sample (SL-GaAs) were then compared with the reference sample of the same structure grown on a GaSb substrate (SL-GaSb). At 80 K, the dark current density and the detectivity values of the pin photodetectors were recorded as 5.40 × 10−3 A cm−2 and 2.34 × 1010 cm Hz0.5 W−1 for the SL-GaAs and 9.50 × 10−4 A cm−2 and 4.70 × 1010 cm Hz0.5 W−1 for the SL-GaSb, respectively.

Decoding of Multilevel Stokes-Vector Modulated Signal by Polarization-Analyzing Circuit on InP

Of-late research on Stokes vector receivers for the short-reach optical communications has gained significant attention due to its capability to decode information in multidimension using cost-effective direct-detection technique. Here, we consider the use of InP for potentially low-cost direct-detection-based Stokes vector (SV) receiver. It consists of a 1 × 4 multimode interference power splitter with different combination of polarization converters on output arms, so that input SV is projected onto distinct vectors on the Stokes space. By using the fabricated device, we experimentally demonstrate decoding of two-level and four-level SV-modulated signals at 3 Gbaud. With the potential of monolithically integrating high-speed InP photodetector array on the same chip, it paves the way to realize compact and low-cost SV receivers for multilevel SV modulation formats in future short-reach optical communication links.

Optical properties of Zn-diffused InP layers for the planar-type InGaAs/InP photodetectors * * Project supported by the Key R&D Program of Jiangsu Province (No. BE2016085) , the National Natural Science Foundation of China (Nos. 61674051), and the External Cooperation Program of BIC, Chinese Academy of Sciences (No. 121E32KYSB20160071).

Zn diffusion into InP was carried out ex-situ using a new Zn diffusion technique with zinc phosphorus particles placed around InP materials as zinc source in a semi-closed chamber formed by a modified diffusion furnace. The optical characteristics of the Zn-diffused InP layer for the planar-type InGaAs/InP PIN photodetectors grown by molecular beam epitaxy (MBE) has been investigated by photoluminescence (PL) measurements. The temperature-dependent PL spectrum of Zn-diffused InP samples at different diffusion temperatures showed that band-to-acceptor transition dominates the PL emission, which indicates that Zn was commendably diffused into InP layer as the acceptor. High quality Zn-diffused InP layer with typically smooth surface was obtained at 580 °C for 10 min. Furthermore, more interstitial Zn atoms were activated to act as acceptors after a rapid annealing process. Based on the above Zn-diffusion technique, a 50 μm planar-type InGaAs/InP PIN photodector device was fabricated and exhibited a low dark current of 7.73 pA under a reverse bias potential of −5 V and a high breakdown voltage of larger than 41 V (I < 10 μA). In addition, a high responsivity of 0.81 A/W at 1.31 μm and 0.97 A/W at 1.55 μm was obtained in the developed PIN photodetector.

Analysis of dark current considering trap-assisted tunneling mechanism for InGaAs PIN photodetectors

In0.53Ga0.47As PIN photodetectors were fabricated and their dark currents were measured. Based on the analysis of different mechanisms, a complete dark current model considering trap-assisted tunneling (TAT) mechanism under low and intermediate reverse bias is constructed by studying the electric fields and carrier generation-recombination rates. The obtained current–voltage experimental results under dark conditions are in good agreement with our simulation using this complete model. The contribution of each mechanism is investigated, and to evaluate the dominant factor deriving from Shockley–Read–Hall generation or TAT, a critical voltage ( $$V_{cri}$$ ) where $$I_{TAT} = I_{SRH} \approx 0.5I_{dark}$$ is proposed. In addition, the effects of thickness and doping concentration of absorption layer on $$V_{cri}$$ are discussed in detail, from which we demonstrate that $$I_{TAT}$$ is the dominant component of dark current for those photodetectors operating under the reverse bias of 5 V if the thickness of absorption layer is less than 1 μm when the doping concentration is 1 × 1015 cm−3, or the doping concentration of absorption layer is more than 7 × 1015 cm−3 when the thickness is 2 μm. The effect of temperature on dark current due to TAT is also analyzed.

Infrared single photon detector based on optical up-converter at 1550\u2009nm

High performance single photon detector at the wavelength of 1550 nm has drawn wide attention and achieved vast improvement due to its significant application in quantum information, quantum key distribution, as well as cosmology. A novel infrared up-conversion single photon detector (USPD) at 1550 nm was proposed to work in free-running regime based on the InGaAs/ InP photodetector (PD)- GaAs/AlGaAs LED up-converter and Si single photon avalanche diode (SPAD). In contrast to conventional In0.53Ga0.47As SPAD, the USPD can suppress dark count rate and afterpulsing efficiently without sacrificing the photon detection efficiency (PDE). A high PDE of ~45% can be achieved by optical adhesive coupling between up-converter and Si SPAD. Using a developed analytical model we gave a noise equivalent power of 1.39 × 10−18 WHz1/2 at 200 K for the USPD, which is better than that of InGaAs SPAD. This work provides a new single photon detection scheme for telecom band.

High-speed 1.3 -1.55 um InGaAs/InP PIN photodetector for microwave photonics

We have fabricated the 1.3-1.55 um PIN photodetector based on InGaAs/InP heterostructure. Measurement results of optical and electrical characteristics of PIN photodetector chip were the following: photoconductivity at 1550 nm was 0.65 A/W and internal capacitance was 0.025 pF. Microwave model of photodetector was developed and verified by measurements of scattering matrix. The implementation of broadband (up to 20 GHz) hybrid integrated matching and biasing circuit for high-speed photodetector is presented.

Optofluidic sensor system with Ge PIN photodetector for CMOS-compatible sensing

Vertical optofluidic biosensors based on refractive index sensing promise highest sensitivities at smallest area foot-print. Nevertheless, when it comes to large scale fabrication and application of such sensors, cheap and robust platforms for sample preparation and supply are needed - not to mention the expected ease of use in application. We present an optofluidic sensor system using a cyclic olefin copolymer microfluidic chip as carrier and feeding supply for a complementary metal-oxide-semiconductor-compatibly fabricated Ge PIN photodetector. Whereas typically only passive components of a sensor are located within the microfluidic channel, here the active device is directly exposed to the fluid, enabling top-illumination. The capability for detecting different refractive indices was verified by different fluids with subsequent recording of the optical responsivity. All components excel in their capability to be transferred to large scale fabrication and further integration of microfluidic and sensing systems. The photodetector itself is intended to serve as a platform for further sophisticated collinear sensing approaches.

Comparison of different etching methods on the morphology and semiconductor characters of black silicon

Femtosecond laser etching, deep reactive ion etching and metal-catalyzed chemical etching are used to fabricate black silicon. It has been found that the light absorption is significantly enhanced in the wavelength of 400∼2200nm, in which the absorption in near infrared band of black silicon etched by femtosecond laser with SF6 has the highest value. It is observed that, however, the minority carrier lifetime of crystalline silicon is shortened to some extent, which can be adjusted and controlled effectively by depositing SiNx film to passivate the surface of black silicon. Finally, a PIN photodetector is manufactured based on black silicon and a higher responsibility of 0.57 A/W at 1060 nm is obtained compared to the PIN silicon photodetector without etching process.

The 8×10 GHz Receiver Optical Subassembly Based on Silica Hybrid Integration Technology for Data Center Interconnection**Supported by the National High Technology Research and Development Program of China under Grant No 2015AA016902, the National Natural Science Foundation of China under Grant Nos 61435013 and 61405188, and the K. C. Wong Education Foundation.

An 8×10 GHz receiver optical sub-assembly (ROSA) consisting of an 8-channel arrayed waveguide grating (AWG) and an 8-channel PIN photodetector (PD) array is designed and fabricated based on silica hybrid integration technology. Multimode output waveguides in the silica AWG with 2% refractive index difference are used to obtain flat-top spectra. The output waveguide facet is polished to 45° bevel to change the light propagation direction into the mesa-type PIN PD, which simplifies the packaging process. The experimental results show that the single channel 1 dB bandwidth of AWG ranges from 2.12 nm to 3.06 nm, the ROSA responsivity ranges from 0.097 A/W to 0.158 A/W, and the 3 dB bandwidth is up to 11 GHz. It is promising to be applied in the eight-lane WDM transmission system in data center interconnection.

Simulation investigation of strained black phosphorus photodetector for middle infrared range.

In this paper, we design the uniaxially and biaxially strained black phosphorus (BP) photodetectors. Different strains applied in the zigzag or armchair direction can effectively tune the direct band gap of 5-layer of BP. The optical field intensity is modeled to determine the absorption for the BP layer. The strain effect on the band structure of BP is investigated using first-principles method based on density functional theory. The cut-off wavelength of strained 5-layer of BP pin photodetector is extended to middle infrared range with a high responsivity of 66.29 A/W, which means that the strained black phosphorus photodetector provides a new approach for the middle-infrared range optoelectronic devices.

Near-infrared laser annealing of Ge layers epitaxially grown on Si for high-performance photonic devices

Near-infrared laser annealing of Ge epitaxial layers on Si is studied as a postgrowth annealing process to reduce the density of threading dislocations (TDs) in Ge. Laser annealing is performed using an exposure of 1.07-μm-laser light with the power density as large as 8 kW/cm2 and the duration as short as 10 ms. The TD density is successfully reduced from 6 × 108 to 2 × 108 cm−2 in a 600-nm-thick Ge layer grown by ultrahigh-vacuum chemical vapor deposition on Si. Vertical pin photodetectors of laser-annealed Ge show a significant reduction of dark leakage current as small as 20 mA/cm2 with a high photodetection efficiency. The short annealing time is effective to prevent the dopant diffusion in Ge together with the Ge-Si intermixing at the interface, being applicable to the annealing even after the formation of pin junctions in Ge. In terms of the reduction of thermal budget, the use of longer wavelength up to ∼1.6 μm has potential applications to preferential annealing of Ge layers on a Si platform due to the strong optical absorption in Ge despite the high optical transparency in Si.

SIMULATIVE INVESTIGATION OF 16X5 GB/S &amp; 16X10 GB/S WDM-FSO TRANSMISSION SYSTEM UNDER DIFFERENT ATMOSPHERIC CONDITIONS

In Free Space Optic (FSO) system free space requires as a communication media. Atmospheric attenuation due to communication media can degrade a system performance. To overcome this losses BER or Q-factor of a system are improved by using different type of photo-detector at receiver side & using optical receiver at link.. This paper describe the design and simulation of 16-channel WDM based Free Space Optical communication link under various Atmospheric conditions at different bit rates (5Gbps/10Gbps) using APD & PIN photo-detector & the performance of system using APD & PIN photo-detector is compared. The NRZ modulation format & semiconductor optical amplifier (SOA) is used in this design. In this simulation it observed that APD photo-detector at bit rate 5Gbps/10Gbpsgive better performance at higher attenuation.

Electrical and optical performances with extracted minority carrier lifetimes of InAs/GaSb SL photodetector operating in the mid wavelength infrared range

We report a study on the temperature dependence of electrical and optical performance of InAs/GaSb based type-II superlattice (T2SL) pin photodetectors in the mid wavelength infrared range (MWIR). The SL structure exhibits an optical response of 50% cut-off wavelength at 4.9 μm at 79 K. Deduced from current density–voltage (J–V) measurements, dark current density under 0.1 V reverse bias is measured as 7.6 × 10−6 A/cm2 with a corresponding differential–resistance–area product (R0A) of 3.3 × 104 Ωcm2 at 100 K. Minority carrier lifetimes of the T2SL detectors are analysed by Shockley's Model where experimental data for dark current densities are fitted by diffusion and generation-recombination (GR) components at different temperatures.

FSO channel estimation for OOK modulation with APD receiver over atmospheric turbulence and pointing errors

In the free-space optical (FSO) links, atmospheric turbulence and pointing errors lead to scintillation in the received signal. Due to its ease of implementation, intensity modulation with direct detection (IM/DD) based on ON–OFF-keying(OOK) is a popular signaling scheme in these systems. For long-haul FSO links, avalanche photo diodes (APDs) are commonly used, which provide an internal gain in photo-detection, allowing larger transmission ranges, as compared with PIN photo-detector (PD) counterparts. Since optimal OOK detection at the receiver requires the knowledge of the instantaneous channel fading coefficient, channel estimation is an important task that can considerably impact the link performance. In this paper, we investigate the channel estimation issue when using an APD at the receiver. Here, optimal signal detection is quite more delicate than in the case of using a PIN PD. In fact, given that APD-based receivers are usually shot-noise limited, the receiver noise will have a different distribution depending on whether the transmitted bit is ‘0’ or ‘1’, and moreover, its statistics are further affected by the scintillation. To deal with this, we first consider minimum mean-square-error (MMSE), maximum a posteriori probability (MAP) and maximum likelihood (ML) channel estimation over an observation window encompassing several consecutive received OOK symbols. Due to the high computational complexity of these methods, in a second step, we propose an ML channel estimator based on the expectation–maximization (EM) algorithm which has a low implementation complexity, making it suitable for high data-rate FSO communications. Numerical results show that for a sufficiently large observation window, by using the proposed EM channel estimator, we can achieve bit error rate performance very close to that with perfect channel state information. We also derive the Cramer–Rao lower bound (CRLB) of MSE of estimation errors and show that for a large enough observation window, this CRLB can be adequately tight.

Design and Simulation of Top Illuminated InGaAs PIN Photodetector for Millimeter-Wave Applications

This paper proposed a newdesign of top illuminated PIN photodetector at 1550nm wavelength for millimeter-wave applications. Device topology, structure and fabrication methods were considered in designing the photodetector. The combination material of InP/InGaAsP/InGaAs/InGaAsP was used in designing the top illuminated PIN photodetector. This PIN photodetector was targeted to produce at least 0.60A/W of responsivity with a dark current of &lt;100nA. The design, layout, and electrical characteristics of this photodetector were carried out using SILVACO TCAD tool. The simulated results show higher responsivity value than targeted, device frequency response of -3dBm at 40GHz with targeted dark current achievable within the wavelength absorption bands specification. The results are compared with similar designs from other reported works.

Fabrication and characterization of high lattice matched InAs/InAsSb superlattice infrared photodetector

We have fabricated the new composition structure high-lattice-matched mid-wave infrared Ga-free InAs/InAs0.73Sb0.27 type-II superlattice (T2SL) pin photodetectors on GaSb substrates. Current-voltage and photocurrent measurements of samples were characterized with different sized mesa structures at 77K. The resulting of mid-infrared photovoltaic detectors measured at 77K exhibit a measured dark current density of 6.13×10−4A/cm2 under a bias of −300mV, a maximum differential-resistance-area-product of 448Ω·cm2 at −47mV bias, a 50% cutoff wavelength of 5.1μm, and a peak responsivity of 0.883 A/W over a mesa size of 50µm×50µm. Peak quantum efficiency of 34.6% at 2.78µm over a mesa size of 50µm×50µm, 23.3% at 2.78µm over a mesa size of 200µm×200µm, and 14.1% at 2.8µm over a mesa size of 300µm×300µm are achieved under zero bias at 77K, respectively.

Characterization of a Ge1-x-ySiySnx/Ge1-xSnx multiple quantum well structure grown by sputtering epitaxy.

A high-quality Ge0.88Si0.08Sn0.04/Ge0.94Sn0.06 multiple quantum well (MQW) structure was grown on a Ge (001) substrate by sputtering epitaxy. The MQW structure was characterized by high-resolution x-ray diffraction and transmission electron microscopy. Surface-illuminated Ge0.88Si0.08Sn0.04/Ge0.94Sn0.06 MQW pin photodetectors were fabricated with cutoff wavelengths of up to 2140nm. The analysis of transitions from spectral response was fitted well with the theoretical calculations. Results suggest that sputtering epitaxy is a promising method for preparing high-quality low-dimensional Sn-based group IV materials and that Ge1-x-ySiySnx/Ge1-xSnx MQWs have potential applications in the development of efficient Si-based photonic devices.