Biased Photodiodes Research Articles

Experimental study of millisecond pulse laser ablation biased silicon-based PIN photodiodes

The investigation of the highest surface temperature and damage region of silicon-based photodiodes (PIN) was conducted through irradiation with millisecond (ms) pulse lasers. The convex spots on the surface of the biased photodiode were observed to be diminished by a millisecond pulse laser for the first time. The experimental results presented herein demonstrate the presence of a bump, even in cases where the maximum surface temperature of the damaged area does not exceed the melting point. The mechanism underlying this phenomenon was elucidated through the integration of simulation and experimentation in our study. The irradiation of silicon-based semiconductor detectors with lasers generates internal Joule heat, causing the temperature at the junction depth to initially reach the melting point. The expansion resulting from the Si phase transition induces outward pressure on Si3N4, leading to the eventual formation of a convex morphology. The findings of our study present a novel approach to enhance the security of photodetectors.

Plasmonic Nanoparticles on Graphene Absorber for Broadband High Responsivity 2D/3D Photodiode.

To overcome the image deterioration caused by pixel miniaturization resulting from the high-resolution trend of CIS (CMOS image sensor) technology, a photodiode working with an enhanced mechanism based on a distinctive device structure from the existing one is considerably required. In this study, our photodiode, consisting of gold nanoparticles/monolayer graphene/n-type trilayer MoS2/p-type Si bulk, achieved ultrafast rising/falling times of 28.6 ns/30.4 ns due to the spatially confined narrow depletion width (DW) resulting from the 2D/3D heterojunction. To compensate for the expected low absorbance due to the narrow DW, plasmonic gold nanoparticles on monolayer graphene are introduced, revealing broadband enhanced EQE of an average of 187% in the spectral range of 420-730 nm and the maximum EQE reaching 847% at 5 nW for a 520 nm wavelength. The broadband enhancement was further investigated through multiphysics simulation, and carrier multiplication in graphene was discussed for the reason for exceeding 100% EQE in our reverse biased photodiode.

Nonlinear optical imaging by detection with optical parametric amplification (invited paper).

Nonlinear optical imaging is a versatile tool that has been proven to be exceptionally useful in various research fields. However, due to the use of photomultiplier tubes (PMTs), the wide application of nonlinear optical imaging is limited by the incapability of imaging under ambient light. In this paper, we propose and demonstrate a new optical imaging detection method based on optical parametric amplification (OPA). As a nonlinear optical process, OPA intrinsically rejects ambient light photons by coherence gating. Periodical poled lithium niobate (PPLN) crystals are used in this study as the media for OPA. Compared to bulk nonlinear optical crystals, PPLN crystals support the generation of OPA signal with lower pump power. Therefore, this characteristic of PPLN crystals is particularly beneficial when using high-repetition-rate lasers, which facilitate high-speed optical signal detection, such as in spectroscopy and imaging. A PPLN-based OPA system was built to amplify the emitted imaging signal from second harmonic generation (SHG) and coherent anti-Stokes Raman scattering (CARS) microscopy imaging, and the amplified optical signal was strong enough to be detected by a biased photodiode under ordinary room light conditions. With OPA detection, ambient-light-on SHG and CARS imaging becomes possible, and achieves a similar result as PMT detection under strictly dark environments. These results demonstrate that OPA can be used as a substitute for PMTs in nonlinear optical imaging to adapt it to various applications with complex lighting conditions.

Enhanced Numerical Modeling of HgCdTe Long Wavelength Infrared Radiation High Operating Temperature Non-equilibrium P+\u03bd(\u03c0)N+ Photodiodes

Using our computer programs, numerical simulations of photoelectric and fluctuating phenomena were carried out in diode structures of the CdHgTe mesa in the P+ν(π)N+ configuration operating at 230 K and 300 K. These phenomena were analyzed in structures where additional energy barriers at the absorber boundary were applied. Exclusion and extraction of charge carriers in the absorber area after biasing the structures with reverse voltage reduces their concentration by more than an order of magnitude. Reduction of carrier concentration has a positive effect on the increase of the absorption coefficient due to reduction of the Burstein–Moss effect, increases the resistance and electro-optical gain, and effectively suppresses generation and thermal recombination. It is possible to obtain 70% of quantum efficiency in biased photodiodes. It was shown that a non-equilibrium long-wave photodiode working at room temperature can have a normalized detectivity of over 109 cmHZ1/2W−1 for radiation with 10.6 μm wavelength. The results of our calculations and their analysis are illustrated by numerous figures.

Spatial intensity profiling of elastic and inelastic scattering in isotropic and anisotropic liquids by immersion of a spherical silicon photocell

The transverse spatial intensity distribution of elastic and inelastic light scattering in passive and active as well as weak and strong scattering liquid media has been studied by using Sphelar One p-n junction silicon spherical photocells. We immersed a Sphelar One in these scattering solutions and measured the photoconductive response in reverse biased photodiode (PD) configuration. The passive weak scattering medium was pure ethanol (EtOH), whereas the passive strong scattering medium was 5CB nematic liquid crystal (NLC). Solutions of 0.1mM Rhodamine 640 perchlorate laser dye in EtOH and in 5CB NLC were used as active scattering media. The response of Sphelar One was strongly enhanced in 5CB NLC compared to EtOH, as well as in active solutions compared to passive solutions. The morphology of the Sphelar One is already advantageous over conventional one-sided planar PDs inside liquid solutions. This omnidirectional response of the Sphelar One can further be enhanced by optimizing the properties of the surrounding passive elastic and active inelastic scatterers.

Signatures of differential Log R–V characteristics for non-uniformity analysis of HgCdTe infrared photodiode arrays

In continuation to our research on the non-uniformity in infrared focal plane arrays of HgCdTe photodiodes, we have examined and found a few important signature parameters in the forward bias region of the electrical characteristics of the photodiodes. These signatures are the peaks of the first and second order derivatives of dynamic resistance–voltage characteristics. They show good correlation with the material and devices parameters and have been investigated to be good signatures for statistical performance variation analysis. In this note, by using theoretical model and statistical analysis of these signatures, we show that the variations in the proposed signatures represent underlying non-uniformity in important material/device parameters. Such signatures may be used along with the other conventional signatures of reverse biased photodiode characteristics to identify the root cause of response non-uniformity in the array with high confidence level.

Implementation of Noise Spectroscopy Using Biased Large-Area Photodiodes

The bremsstrahlung X-ray spectrum produced by X-ray sources used in cargo inspection systems is attenuated and modified by materials in the cargo in a Z-dependent way and then detected in a radiographic detector array. We have previously shown that it is possible to obtain spectral information indirectly by analyzing statistical fluctuations (the “noise”) in radiographic data, in a technique we call Noise Spectroscopy (NS) or Z-SCAN (Z-determination by Statistical Count-rate ANalysis). The technique is especially effective when the detector array consists of fast scintillation detectors and waveform digitization electronics, measuring both the waveform mean and variance during each X-ray pulse. This previous work, however, used photo-multiplier tubes, which are not especially suitable for a practical implementation. Here we describe the results of R&D performed to produce an effective version of the technique that lends itself to implementation in a single detector array that can be used both for radiography and for NS, with the same imaging spatial resolution as in conventional systems. We characterize the performance of biased photodiodes in combination with trans-impedance preamplifiers, read out with commercially available waveform digitizers. We report on experiments performed with a 16-channel detector array in a test beam, with test samples of different atomic number Z. We also report the implementation of an NS algorithm in an FPGA. In combination, we show that a practical implementation of Noise Spectroscopy in cargo inspection systems is feasible.