Heterojunction Photodiodes Research Articles

Characterization and modeling of a-Si:H-based n-i-p photodiodes with protocrystalline silicon p-layers

This article reports on blue-enhanced a-Si:H-based n-i-p photodiodes with protocrystalline silicon (pc-Si:H) p-layers by plasma-enhanced chemical vapor deposition. Microstructure of p-layers was studied by Raman spectroscopy. An optical model has been developed to analyze the device performance. The Transfer Matrix Method was applied to simulate light propagation in the glass/Cr/n-i-p/ZnO:Al stack, while modified Tauc-Lorentz model including the Urbach tail was used to obtain the dispersive optical constants for each semiconductor layer. Two photodiodes with a-Si:H and pc-Si:H p-layers were fabricated, characterized, and modeled for comparison. The deduced optical gaps are 1.8 and 2.33 eV for p-type a-Si:H and pc-Si:H, respectively. Observed band gap widening is the quantum confinement effect due to Si nanocrystals in pc-Si:H. Modeling reveals that incorporation of pc-Si:H leads to a significant reduction of absorption and reflection losses. The optimized heterojunction photodiode exhibits a quantum efficiency up to 92% at 510 nm wavelength. The achieved quantum efficiency of 66% at 400 nm wavelength almost triples that for the homojunction photodiode.

Methyl ammonium iodide via novel PECVD process for the growth of 2-step vacuum based perovskite (MAPbI3) thin films

MAPbI3 thin films were grown via 2-step vacuum based processes by depositing methyl ammonium iodide (MAI) layer as first step using plasma enhanced chemical vapour deposition (PECVD) technique and then depositing lead iodide (PbI2) layer over it as second step using RF-sputtering technique. To the best of our knowledge MAI layer was deposited for the first time by PECVD technique. MAI solution for PECVD process and PbI2 target for sputtering process were made to deposit these two layers under optimized plasma conditions for the growth of MAPbI3 thin films. Characterization techniques like UV-Vis-NIR spectroscopy and Photoluminescence spectroscopy were performed to study the optical properties. Powder-XRD (PXRD) and glancing incidence XRD (GIXRD) were performed to study structural properties. SEM and cross-SEM were performed for morphological study to view top-view and cross-sectional view of the deposited MAPbI3 perovskite thin film. Perovskite thin films deposited on silicon wafer have been used as perovskite/silicon heterojunction photodiode exhibiting critical performance parameters such as rectifying ratio of 1.58 × 104 at 1.0 V, photo-sensitivity value 7.46 × 102 at light intensity 100 mw/cm2 without biasing.

Near-Infrared CMOS Image Sensors Enabled by Colloidal Quantum Dot-Silicon Heterojunction

The solution processibility of colloidal quantum dots (CQDs) promises a straightforward integration with Si readout integrated circuits (Si-ROCIs), which enables a near-infrared (NIR) CMOS image sensor (CIS; CMOS stands for complementary metal-oxide semiconductor). Previously demonstrated CQD NIR CISs were achieved through integrating CQD photodiode or PhotoFET with Si-ROCIs. Here, we conduct a simulation study to investigate the feasibility of a NIR CIS enabled by another integration strategy, that is, by forming a CQD-Si heterojunction. Simulation results clearly show that each active pixel made of CQD-Si heterojunction photodiode on the CIS sensitively responds to NIR light, and generated photocarriers induce changes in electrostatic potentials in the active pixel. The potential changes are read out through the integrated circuits as validated by the readout timing sequence simulation.

A self-powered UV–vis–NIR graphite/CdZnTe Schottky junction photodiode

We proposed a self-powered UV–vis–NIR Schottky junction photodiode based on a unique combination of radiation-hard functional materials: thin-film semi-metal Graphite and CdZnTe single-crystal compound semiconductor. The graphite/CdZnTe Schottky junction photodiodes exhibit a maximum responsivity of 0.25 A W−1 and detectivity of 6.5 × 1011 Jones, close to the best heterojunction photodiodes based on CdZnTe solid solution. The devices are also characterized by short rise/fall times (1.2/7.2 µs) and a wide linear dynamic range (77 dB). The proposed photodiodes are promising for applications in space and terrestrial areas with high levels of ionizing radiation.

High-performance and broadband 2D ReS2/MoS2 semivertical heterojunction photodiodes

The emergence of two-dimensional van der Waals heterostructures has overcome the limitations of conventional heterostructure lattices and materials, opening new possibilities for the development of micro- and nanoscale photodiodes. To achieve a balance between the response speed and sensitivity in two-dimensional photodetectors, we designed a 2D ReS2/MoS2 semivertical heterojunction photodiode with a unilateral depletion region. This photodiode exhibits excellent self-powered capability, a broadband photovoltaic response of 532-785 nm, high responsivity (0.197A/W), power conversion efficiency (2.1%) and detectivity (10⩍12 Jones). In particular, the photodiode achieves an ultra-fast response time of 13/15 μs, enabling a detectable signal cut-off frequency of over 45 kHz. To further enhance the sensitivity of the photodiode under photovoltaic operation, we applied a layer of photosensitive PbS quantum dots (QDs) to the heterojunction and observed an approximately 21% improvement in device responsivity under 532 nm illumination. These findings highlight the potential of ReS2/MoS2 heterostructures for applications in high-performance photodiodes as well as solar cells.

A silver nanoparticle (AgNP)-loaded Bi2Se3 topological insulator p-n heterojunction photodiode for a near-infrared (NIR) photodetector

Near-infrared (NIR) photons are expanding advanced applications in optoelectronics. However, while 2D materials like graphene offer an attractive route for NIR photodetection, the alternative for high-performance NIR detection is still evolving. Hence, solution-processed n-Bi2Se3 /p-Si-based 2D heterojunction photodiodes have been fabricated here and used for high-performance NIR detection. Further, we report high photoresponsivity of 248 mA W−1 at 1100 nm, high external quantum efficiency of 22, 23 and 28% for Ag-loaded (at 5, 7.5 and 10%) Bi2Se3 and good stability. The chemical states of Bi2Se3 and Ag are detected using the core-level spectra of x-ray photoelectron spectroscopy. Photoresponse I–V characteristics are investigated under both dark and illumination; the high photocurrent achieved for Ag-loaded Bi2Se3 and the increase in the forward photocurrent under both dark and bright conditions are reported. The temporal photoresponse curve confirms the good stability (photoswitching behavior) and reproducibility with a response time of 0.74 s and a decay time of 0.18 s. Therefore, these unique performance and device parameters of a manufactured photodiode strongly recommend as a potential heterojunction photodiode for an NIR photodetector.

Photovoltaic Response of Heterojunction Photodiode based on Ba0.8Sr0.2TiO3 Nanorod Film

The BST/Si photodiode has been effectively synthesized by growth BST on the p-type Si (100) substrate utilizing the hydrothermal process. Screen printing was used to prepare TiO2 film deposited on Si substrate, then immersing TiO2 film in Ba(OH)2 and Sr(OH)2 solution to fabricate BST/Si photodiode using a hydrothermal process. The BST film was studied using XRD, FESEM, and reflection spectra. The band gap was calculated for a BT film using the reflection methods. Hall measurement confirmed the n-type conductivity of BST film. Curie temperature of the BST film was observed at 87 °C according to DC measurement. The dark and illuminated (J-V) characteristics of the BST/Si photodiode have been measured under simulated AM1 conditions using a Xenon lamp. The Shockley-Read- Hall recombination caused unequal electron and hole capture rates that dominated the I-V characteristics resulting in an absence of classic superposition phenomena. The open circuit voltage (Voc) measurement is carried out to know the recombination mechanism in an open circuit. The BST/Si film showed more conductivity after increasing illuminating power density, which qualifies it for photovoltaic applications.

On the Piezophototronic Effect in Heterojunction Photodiode with Type‐II Energy Band: Theoretical Model for Anisotype Heterojunction

The piezophototronic effect has been widely explored to improve the performance of optoelectronic devices. However, modulation of piezoelectric charges varies with different energy band structures. Thus, it is important to investigate the specific role of the piezophototronic effect from a theoretical perspective. Herein, the piezophototronic effect in anisotype p‐Si/n‐ZnO heterojunction photodiodes with type‐II energy band diagrams through analytical derivation and numerical simulation is thoroughly studied. It is found that both the depletion region and quasineutral region have a decisive effect on photocurrent in their respective regions. Specifically, modulations of piezoelectric charges on depletion region current and quasineutral region current are opposite and compensate each other, resulting in reduced piezophototronic effect. Heterojunctions under short diode conditions are preferred for better piezophototronic effect as modulation on quasineutral region current is weakened while that on depletion region current remains unchanged. The effects of doping concentration, absorption coefficient, and minority carrier lifetime of semiconductor materials on device characteristics are also studied. This work provides deeper insight into the underlying device physics of the piezophototronic effect.

High-Performance Photodetectors With Polarization Sensitivity Based on p-n and p-p+ Black Phosphorus/Germanium Heterojunctions

The heterostructures between atomically thin 2-D and 3-D semiconductors show great potential for high-performance photodetector. In this work, the efficient light detection of the p-n and p-p+ black phosphorus (bP)/germanium (Ge) heterojunction photodiode has been demonstrated. With the change of Ge doping type, the rectification direction of the heterojunction diode formed by bP and Ge could be reversed. Due to the enhanced photocarrier separation at the reverse bias, the bP/n-Ge (bP/p-Ge) device has a responsivity of 6.08 (3.43) A/W under 1550-nm illumination, with fast response speed in the 10- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> level. The bP/n-Ge device has a significant photovoltaic effect due to the small conduction band energy offset, with a large open-circuit voltage of 0.34 V. Under the illumination of light with different polarization directions, the device exhibits apparent polarization-sensitive detection, and the dichroic ratio of bP/n-Ge and bP/p-Ge devices is 4.25 and 3.85, respectively. These results suggest that the bP/Ge heterojunction photodetector would have great potential in high-performance, self-powered, and polarization-sensitive photodetection.

Analysis of Electrical Characteristics of N-Doped TiO2 and Si Heterojunction Diodes

Heterojunction photodiodes play a crucial role in various industries and daily life. They find application in fields such as photoelectric detection, aerospace, and intelligent manufacturing. In this study, we employed a series of growth processes, including physical vapor deposition techniques such as magnetron sputtering, high-temperature annealing, and hydrothermal growth, to fabricate N-doped TiO2 heterojunction diode devices with Si as a substrate material. The surface of the device exhibited a columnar array structure with rutile phase TiO2. Additionally, the doping of N element led to the bending of the energy band of TiO2 by approximately 0.2 eV, and the Fermi level also shifted to the valence band, without any effect on the band gap. The I–V characteristics varied in vacuum and air, with ideal factors (η) of 4.1 and 8.72, respectively. The study is expected to broaden the application scope of doped photodiodes.

MoSe2/WS2 heterojunction photodiode integrated with a silicon nitride waveguide for near infrared light detection with high responsivity

We demonstrate experimentally the realization and the characterization of a chip-scale integrated photodetector for the near-infrared spectral regime based on the integration of a MoSe2/WS2 heterojunction on top of a silicon nitride waveguide. This configuration achieves high responsivity of ~1 A W−1 at the wavelength of 780 nm (indicating an internal gain mechanism) while suppressing the dark current to the level of ~50 pA, much lower as compared to a reference sample of just MoSe2 without WS2. We have measured the power spectral density of the dark current to be as low as ~1 × 10−12 A Hz−0.5, from which we extract the noise equivalent power (NEP) to be ~1 × 10−12 W Hz−0.5. To demonstrate the usefulness of the device, we use it for the characterization of the transfer function of a microring resonator that is integrated on the same chip as the photodetector. The ability to integrate local photodetectors on a chip and to operate such devices with high performance at the near-infrared regime is expected to play a critical role in future integrated devices in the field of optical communications, quantum photonics, biochemical sensing, and more.

Formation of Micro‐Patterned Ga2O3/Se Heterojunction and its Application to Highly Sensitive Avalanche Photodiode

Micropatterned Heterojunction Photodiodes In article number 2200636, Yusuke Adachi and Taizo Kobayashi developed micropatterned photodiodes using selenium thin films which exhibit high optical absorption at visible wavelengths. Ga2O3/Se heterojunction avalanche photodiodes are miniaturized to square-shaped micropatterns at 100 μm2. Photocurrent density is increased with decreasing the active area, and the highest external quantum efficiency of 330% is observed at a bias voltage of 15 V at the active area of 100 μm2.

ZnO hole blocking layer induced highly UV responsive p-NiO/n-ZnO/n-Si heterojunction photodiodes

ZnO hole blocking layer induced highly UV responsive p-NiO/n-ZnO/n-Si heterojunction photodiodes

A High‐Detectivity, Fast‐Response, and Radiation‐Resistant TiN/CdZnTe Heterojunction Photodiode (Advanced Optical Materials 2/2023)

Photodiodes have found wide practical applications as sensing and information transmission technology in different environments. Viktor Brus and co-workers (article number 2202028) report a novel high-performance UV-vis-NIR heterojunction photodiode based on radiation-resistant functional semiconductor materials: TiN ‘window’ layer and CdZnTe photoactive layer. This work pushes the current detectivity–response time boundaries, defined by the long-standing materials science and device engineering problems in developing concurrently highly sensitive, fast-responding, and radiation-resistant optoelectronic devices based on compound semiconductors.

Numerical study and design of high-efficiency p-In0.1Ga0.9N/i-GaN/n-GaN heterojunction photodiode

This paper reports the performance of a proposed GaN heterojunction p-i-n photodiode with a p-type In0.1Ga0.9N layer. The simulation results show that, compared with the GaN homojunction p-i-n structure, the GaN heterojunction p-i-n structure performs better on the basis of such simulations as photocurrent density and responsivity. The effects of reverse bias voltage, light intensity and i-GaN absorbing layer thickness are explored. The peak responsivity and the cutoff frequency are found to increase remarkably with increasing reverse bias voltage. The degradation of device responsivity and cutoff frequency at high optical excitation power density are also investigated. By increasing the i-GaN absorbing layer thickness, responsivity increases but cutoff frequency decreases. The maximum responsivity is 0.3 A/W at 0.363 μm under an illumination intensity of 105 W/cm2 and an applied reverse bias voltage of −2 V, while the highest cutoff frequency 12 GHz is achieved at an applied reverse bias voltage of −14 V.

Identification of the Origin of Ultralow Dark Currents in Organic Photodiodes.

Organic bulk heterojunction photodiodes (OPDs) attract attention for sensing and imaging. Their detectivity is typically limited by a substantial reverse bias dark current density Jd . Recently, using thermal admittance or spectral photocurrent measurements, Jd has been attributed to thermal charge generation mediated by mid-gap states. Here, we report the temperature dependence of Jd in state-of-the-art OPDs with Jd down to 10-9 mA cm-2 at -0.5V bias. For a variety of donor-acceptor bulk-heterojunction blends we find that the thermal activation energy of Jd is lower than the effective bandgap of the blends, by ca. 0.3 to 0.5eV, but higher than expected for mid-gap states. Ultra-sensitive sub-bandgap photocurrent spectroscopy reveals that the minimum photon energy for optical charge generation in OPDs correlates with the dark current thermal activation energy. The dark current in OPDs is attributed to thermal charge generation at the donor-acceptor interface mediated by intra-gap states near the band edges. This article is protected by copyright. All rights reserved.

A High‐Detectivity, Fast‐Response, and Radiation‐Resistant TiN/CdZnTe Heterojunction Photodiode

AbstractA novel high‐performance ultraviolet–visible–near‐infrared (300–820 nm) heterojunction photodiode based on radiation‐resistant semiconductor materials is proposed. A titanium nitride (TiN) “window” layer is deposited via magnetron sputtering onto a cadmium zinc telluride (CdZnTe) solid solution single crystal. The TiN/CdZnTe heterojunction photodiodes concurrently reveal an outstanding detectivity, response time, and linear dynamic range outperforming similar heterojunction photodiodes and photodetectors, based on photoactive inorganic compound semiconductor materials. Moreover, the added feature of the proposed heterojunction photodiodes is their excellent radiation resistance, experimentally demonstrated under short impulse proton irradiation (170 keV) with an accumulated fluence of 2 × 1012 proton cm−2. This unusual synergy of high performance and advanced radiation resistance of the TiN/CdZnTe photodiodes provides a unique platform for operation in space or radioactively contaminated environments.

Polarization-induced photocurrent switching effect in heterojunction photodiodes

Polarization-induced photocurrent switching effect in heterojunction photodiodes

Tuning of photovoltaic response in multiferroic heterojunction photodiodes by a built-in electric field and carrier transport: Effect of magnetization and ferroelectric polarization

Photovoltaic devices consisting of multiferroic thin films have been studied extensively for carrier separation regulated by a built-in electric field and the above bandgap. Here, a novel photodiode with photoelectric conversion efficiency (PCE) of 3.70% by introducing TiO2 and NiOx:5%Cu as the electron and the hole transport layers (ETL/HTL) on both sides of multiferroic bismuth layered perovskite oxide Bi2FeCrO6/Bi6Fe1.6Co0.2Ni0.2Ti3O18 (BFCO/BFCNT) heterojunction with the appropriate band gap were reported based on our recent studies. The results showed that BFCNT displays an Aurivillius structure, but BFCO is of a double perovskite, the bandgaps are ∼1.62 eV and 1.74 eV, respectively. The open-circuit voltage, short-circuit current density, and fill factor of the devices are 0.73 V, 10.5 mA·cm-2, and 48.3% separately under the illumination of 100 mW·cm-2 simulated AM 1.5 G solar light. Investigations of the effects of both external electric and magnetic fields on the photovoltaic responses delivered that the magnetization and ferroelectric polarization can effectively tune the built-in electric field and the carrier transport in multiferroics, thus offering an experimental and theoretical basis for further improving the performance of multiferroic photovoltaic devices.

Facilely Achieved Self-Biased Black Silicon Heterojunction Photodiode with Broadband Quantum Efficiency Approaching 100.

Photodiodes are fundamental components in modern optoelectronics. Heterojunction photodiodes, simply configured by two different contact materials, have been a hot research topic for many years. Currently reported self-biased heterojunction photodiodes routinely have external quantum efficiency (EQE) significantly below 100% due to optical and electrical losses. Herein, an approach that virtually overcomes this 100% EQE challenge via low-aspect-ratio nanostructures and drift-dominated photocarrier transport in a heterojunction photodiode is proposed. Broadband near-ideal EQE is achieved in nanocrystal indium tin oxide/black silicon (nc-ITO/b-Si) Schottky photodiodes. The b-Si comprises nanostalagmites which balance the antireflection effect and surface morphology. The built-in electric field is explored to match the optical generation profile, realizing enhanced photocarrier transport over a broadband of photogeneration. The devices exhibit unprecedented EQE among the reported leading-edge heterojunction photodiodes: average EQE surpasses ≈98% for wavelengths of 570-925nm, while overall EQE is greater than ≈95% from 500 to 960nm. Further, only elementary fabrication techniques are explored to achieve these excellent device properties. A heart rate sensor driven by nanowatt faint light is demonstrated, indicating the enormous potential of this near-ideal b-Si photodiode for low power consuming applications.