Si Heterojunction Photodetector Research Articles

Broadband high-performance vertical WS1.08Se0.92/Si heterojunction photodetector with MXene electrode

Vertical semiconductor van der Waals heterojunctions are essential for fabricating high-performance photodetectors. However, the range of the spectral response and defect states of semiconductor materials are two critical factors affecting the performance of photodetectors. In this work, the spectral response range of WS2 was changed through WS2 band gap regulation, and a self-powered vertical WS1.08Se0.92/Si heterojunction photodetector with MXene electrode was prepared by synthesizing WS1.08Se0.92 film on Si substrate and vertically stacking Ti3C2T x MXene on the film. Due to the electron collection of MXene and the wonderful junction quality of WS1.08Se0.92/Si, the photodetector can detect near-infrared light in the range of 980–1310 nm, which exceed the detection limit of WS1.08Se0.92. And the device had high sensitivity in the broadband. The responsivity was 4.58 A W−1, the specific detectivity was 4.58 × 1011 Jones, the on/off ratio was 4.95 × 103, and the fast response time was 9.81/9.03 μs. These properties are superior to previously reported WS2-based photodetectors. Vertical structure, Energy band tuning, and MXene electrode provide a new idea for preparing broadband high-performance and self-powered photodetector.

Facile fabrication of amorphous-In2Se3/Si heterojunction for fast ultraviolet to near-infrared broadband photodetection

Indium selenide (In2Se3) has emerged as a promising candidate for broadband photodetection due to its suitable bandgap, high electron mobility, high optical absorption coefficient, and broad-spectrum absorption properties. Nevertheless, wafer-scale growth of single-component and pure-phase In2Se3 films remains challenging and requires stringent experimental parameters. Here, a facile approach for depositing amorphous-In2Se3 (a-In2Se3) on Si substrate by physical vapor deposition (PVD) process is proposed to fabricate high-performance a-In2Se3/Si heterojunction photodetectors. The as-produced devices are sensitive to a broad-spectrum (255–1300 nm), exhibiting superior overall performance with a low dark current of 0.54 nA, large current on/off ratio of 2.26 × 104, fast response with rise/decay time of 176/175 μs, decent responsivity of 1.50 A/W and detectivity of 6.46 × 1012 Jones under 1050 nm illumination at − 3 V bias. Such remarkable results can be attributed to the unique type-Ⅰ straddling energy band alignment and the strong coupling between a-In2Se3 and Si interface. In addition, decent responsivity and detectivity under 255 nm (0.29 A/W and 1.25 × 1012 Jones) and 630 nm (0.77 A/W and 3.32 × 1012 Jones) remedy the deficiency of Si in ultra-violet and visible light detection. Our work provides a facile and low-cost route for the realization of high-performance broadband photodetectors based on a-In2Se3/Si heterojunctions.

Ferroelectrically Modulated and Enhanced Photoresponse in a Self-Powered α-In2Se3/Si Heterojunction Photodetector.

Photodetectors have been applied to pivotal optoelectronic components of modern optical communication, sensing, and imaging systems. As a room-temperature ferroelectric van der Waals semiconductor, 2D α-In2Se3 is a promising candidate for a next-generation optoelectronic material because of its thickness-dependent direct bandgap and excellent optoelectronic performance. Previous studies of photodetectors based on α-In2Se3 have been rarely focused on the modulated relationship between the α-In2Se3 intrinsic ferroelectricity and photoresponsivity. Herein, a simple integrated process and high-performance photodetector based on an α-In2Se3/Si vertical hybrid-dimensional heterojunction was constructed. Our photodetector in the ferroelectric polarization up state accomplishes a self-powered, highly sensitive photoresponse with an on/off ratio of 4.5 × 105 and detectivity of 1.6 × 1013 Jones, and it also shows a fast response time with 43 μs. The depolarization field generated by the remanent polarization of ferroelectrics in α-In2Se3 provides a strategy for enhancement and modulation of photodetection. The negative correlation was discovered because the enhancement photoresponsivity factor of ferroelectric modulation competes with the photovoltaic behavior within the α-In2Se3/Si heterojunction. Our research highlights the great potential of the high-efficiency heterojunction photodetector for future object recognition and photoelectric imaging.

Self-Powered, Broadband Photodetector Based on Two-Dimensional Tellurium-Silicon Heterojunction.

As a new class of two-dimensional (2D) materials and a group-VI chalcogen, tellurium (Te) has emerged as a p-type semiconductor with high carrier mobility. Potential applications include high-speed opto-electronic devices for communication. One method to enhance the performance of 2D material-based photodetectors is by integration with a IV group of semiconductors such as silicon (Si). In this work, we demonstrate a self-powered, high-speed, broadband photodetector based on the 2D Te/n-type Si heterojunction. The fabricated Te/n-type Si heterojunction exhibits high performance in the UV-vis-NIR light with a high responsivity of up to ∼250 mA/W and a photocurrent-to-dark current ratio (I on/I off) of ∼106, fast response time of 8.6 μs, and superior repeatability and stability. The results show that the fabricated Te/n-type Si heterojunction photodetector has a strong potential to be utilized in ultrafast, broadband, and efficient photodetection applications.

Fabrication and Characterization of Visible to Near-Infrared Photodetector Based on Multilayer Graphene/Mg2Si/Si Heterojunction.

In this investigation, p–Mg2Si/n–Si heterojunction photodetector (PD) is fabricated by magnetron sputtering and low vacuum annealing in the absence of argon or nitrogen atmosphere. Multilayer Graphene (MLG)/Mg2Si/Si heterojunction PD is first fabricated by transferring MLG to Mg2Si/Si heterojunction substrate using the suspended self-help transfer MLG method. After characterizing the phase composition, morphology and detection properties of Mg2Si/Si and MLG/Mg2Si/Si heterojunction PDs, the successful fabrication of the Mg2Si/Si and MLG/Mg2Si/Si heterojunction PDs are confirmed and some detection capabilities are realized. Compared with the Mg2Si/Si heterojunction PD, the light absorption and the ability to effectively separate and transfer photogenerated carriers of MLG/Mg2Si/Si heterojunction PD are improved. The responsivity, external quantum efficiency (EQE), noise equivalent power (NEP), detectivity (D*), on/off ratio and other detection properties are enhanced. The peak responsivity and EQE of the MLG/Mg2Si/Si heterojunction PD are 23.7 mA/W and 2.75%, respectively, which are better than the previous 1–10 mA/W and 2.3%. The results illustrate that the fabrication technology of introducing MLG to regulate the detection properties of the Mg2Si/Si heterojunction PD is feasible. In addition, this study reveals the potential of MLG to enhance the detection properties of optoelectronic devices, broadens the application prospect of the Mg2Si/Si-based heterojunction PDs and provides a direction for the regulation of optoelectronic devices.

Self-powered broadband α-MoO3/Si photodetector based on photo-induced thermoelectric effect

As a two-dimensional crystal, molybdenum trioxides (α-MoO 3 ) has been considered as a typical candidate for next-generation photodetectors (PDs) but with limited photodetection applications in the ultraviolet region. Here, a photo-induced thermoelectric (PTE) effect in α-MoO 3 is proposed as a practical approach to realize the broadband photodetection of α-MoO 3 /Si heterojunction PDs. High-quality α-MoO 3 films are grown on Si by using an e-beam evaporation method. By modulating the photo-induced thermoelectric potential along the c-axis on the transport properties, the α-MoO 3 /Si PDs can be operated as a self-powered device, showing broadband photoresponse beyond the bandgap limitation in the wavelength range of 405–1550 nm. The manipulation of the PTE effect in the heterojunction is investigated carefully, clarifying the corresponding physical mechanisms of the unique photoresponse behaviors. Furthermore, the fabricated device exhibits competitive photodetection performance with a high photoresponsivity of 63.3 mA/W, a high optical detectivity of 3.1 × 10 11 cm Hz 1/2 W −1 , fast response speeds with the rise/fall times of 0.47/0.76 ms, as well as high durability and environmental stability under 980-nm infrared illumination. These results not only provide a novel strategy to develop novel PDs with high performance, but also supply a deeply understanding of the PTE effect in α-MoO 3 /Si heterojunctions.

Fabrication and properties of a solar-blind ultraviolet photodetector based on Si-doped β-Ga2O3 film grown on p-Si (111) substrate by MOCVD

A solar-blind ultraviolet photodetector based on p-Si/n-β-Ga2O3:Si heterojunction, using the Si-doped β-Ga2O3 as the n-type layer, was fabricated successfully by metal-organic chemical vapor deposition (MOCVD). The current-voltage and photoresponse characteristics of photodetector were investigated. The fabricated p-Si/n-β-Ga2O3:Si heterojunction photodetector exhibited typical rectification behavior and good solar-blind ultraviolet photoresponse. Sensitive photodetection of current at the reverse bias voltage and stable on-off switching performance were achieved. The photodetector showed a responsivity of 3.76 A/W and a photo-to-dark current ratio of 37.9 under 254 nm illumination. The rise time constants (τr1, τr2) and the decay time constants (τd1, τd2) of the photodetector under 254 nm illumination at the reverse voltage of − 20 V were estimated to be (0.30 s, 0.76 s) and (0.15 s, 6.15 s), respectively. The fabricated p-Si/n-β-Ga2O3:Si heterojunction photodetector displayed relatively faster response speed compared to the reported photodetectors based on p-Si/undoped β-Ga2O3 heterojunction. The results indicate that photodetectors based on p-Si/n-β-Ga2O3:Si heterojunction have potential development for the high-performance solar-blind ultraviolet photodetectors.

Preparation of nanostructured cerium-doped MnS/Si heterojunction photodetector by chemical spray pyrolysis: Influence of doping concentration

We report on the preparation of MnS/Si and cerium-doped MnS /Si heterojunction photodetectors by spray pyrolysis technique. The effect of doping concentration on the structural, optical and electrical properties of the MnS film was investigated. X–ray diffraction (XRD) data show that the pure MnS film was crystalline with mixed α-MnS and γ-MnS phases and the doped films exhibited poor crystallinity. Scanning electron microscope (SEM) results illustrate that the film doped with 1 wt% Ce has nanowires morphology, while the other films have spherical grains morphology. Energy dispersive x-ray (EDX) and elemental mapping showed the presence of cerium, magnesium and sulfur elements. The optical transmittance of the film decreases as doping concentration increase. The optical energy gap of decreased from 2.8 eV to 2.58 eV after cerium doping with 3 wt%. Raman spectra of pure MnS and Ce-doped MnS films revealed the presence of vibration mode at 365 and 635 cm−1. The electrical resistivity and mobility of the film after doping with different contents of Ce were measured. The figures of merit of the MnS:Ce/Si heterojunction photodetector as a function of doping concentration were investigated. The current-voltage characteristics under dark and illuminated conditions were investigated. The maximum responsivity was 0.71 A/W at 350 nm for the Mn:Ce (1 wt%)/Si photodetector.

ZnO/Al2O3/p-Si/Al2O3/CuO heterojunction NIR photodetector with inverted-pyramid light-trapping structure

Micro and nano light-trapping structures are widely applied to improve the performance of optoelectronic devices. In this work, inverted-pyramid light trapping texture on industrial-sized p-type silicon was prepared by a rapid and repeatable one-step room-temperature Cu-MACE process. On this basis, various TMOs (transition metal oxide)-Si heterojunction photodetectors (PDs) are fabricated by a low-temperature process. After careful comparison, a ZnO/Al2O3/p-Si/Al2O3/CuO heterojunction is selected as the ideal device structure, and the corresponding work mechanism is proposed. Finally, by optimizing the Al2O3 tunneling layers’ thickness, a high-performance NIR PD working at 980 nm and −5 V bias stands out. The bifacial carrier selective transportation PD exhibits a considerable detectivity (5.56 × 1011 Jones) and a high responsivity (7.10 A/W). Our work will expand the application of inverted-pyramid textured silicon and will pave a road for mass fabrication of TMOs-Si heterojunction PD.

Fabrication and characterization of high photosensitivity CuS/porous silicon heterojunction photodetector

This study focused on the fabrication and characterization of CuS/porous Si heterojunction photodetector prepared by deposition of chemically sprayed CuS film on the porous silicon substrate prepared by anodization method. The optical and structural of CuS film and porous silicon PSi layer were investigated using x-ray diffraction, scanning electron microscope SEM, energy dispersive x-ray EDX, atomic force microscopy AFM, and UV-V–vis optical absorption. XRD studies confirm the CuS film deposited on glass substrate was polycrystalline in nature with hexagonal structure, while the XRD data of the CuS film deposited on PSi shows only single peak at 2θ = 27° corresponds to (101) plane. The optical properties results reveal that the direct optical bandgap of CuS was around 2.25 eV. SEM shows that the average wall size and pore size of the porous silicon were 200 nm and 550 nm, respectively, and the CuS film consists of spherical grains with average grain size of 45 nm. AFM data illustrates that the root mean square of surface roughness of CuS film 9.1 nm. PL spectrum of PSi shows a strong emission peak at 576 nm. The optoelectronics properties of CuS/PSi/c-Si photodetector including dark and illuminated I-V characteristics, spectral responsivity, quantum efficiency, and detectivity were measured at room temperature. The responsivity of the photodetectors at peak of response 500 nm was 2.15 A/W.

Preparation of visible-enhanced PbI2/MgO/ Si heterojunction photodetector

Fabrication and characterization of p-PbI2/MgO/n-Si photodetectors by pulsed laser deposition PLD under different deposition temperatures Ts were demonstrated for the first time. Structural, optical and morphological properties of nanostructured MgO and PbI2/MgO films were investigated using x-ray diffraction XRD, UV–vis absorption and scanning electron microscope SEM. The XRD results revealed a single crystalline MgO with cubic structure along the (200) plane, while the PbI2 film deposited on MgO was a single crystalline with hexagonal phase along (001) plane. The optical energy gaps of PbI2 films deposited on MgO film were found to be within (2.7-2.5) eV. The current-voltage and capacitance-voltage properties of PbI2/MgO/Si photodetector were investigated. The best responsivity of p-PbI2/MgO/n-Si photodetectors was ∼ 0.88A/W at 410 nm when the photodetector was prepared at Ts =45 °C.

Implementation of lateral Ge–on–Si heterojunction photodetectors via rapid melt growth and self-aligned microbonding for Si photonics

Heterogeneous integration of Ge on a Si lateral p–i–n junction by rapid melt-growth method and self-aligned microbonding is presented. A very thin Ge (100 nm) strip butt-coupled to a Si waveguide for implementing a waveguide photodetector is reported with a low dark current of 1 nA at −3 V bias. The measured 3 dB cut off frequency for the photodetectors is 30 GHz. The internal device responsivity is estimated to be 0.72 A W−1 at the reverse bias of 3 V.

Hybrid p-Au@PbI2/n-Si heterojunction photodetector prepared by pulsed laser ablation in liquid

In this study, a hybrid Au@PbI2/Si heterojunction photodetector was prepared by laser ablation in liquid technique at different number laser pulses. The electrical properties of Au@PbI2/Si heterojunction were measured as a function of the number of laser pulses. The dark current-voltage characteristics showed that fabricated heterojunctions exhibited rectification properties and the largest value of rectification factor at 5 V bias was ˜35 for heterojunction prepared at 100 laser pulses. Hall effect measurements reveal that all synthesized Au@PbI2 have p-type conduction and its Hall mobility decreases as the number of laser pulses increase. The ideality factor and the turn-on voltage of heterojunctions were determined as a function of the number of laser pulses. Capacitance-voltage characteristics of the heterojunctions confirm that all the heterojunctions are abrupt and the value of built-in-potential was ranged from 0.3 to 0.8 V depending on the number of laser pulses. The effect of the number of laser pulses on the figures of merit of the hybrid Au@PbI2/Si heterojunction photodetector namely; responsivity, external quantum efficiency, detectivity and minority carrier lifetime was studied. The responsivity of the photodetector shows a presence of two response peaks located at visible and near-infrared regions which are related to the absorption edge of Au@PbI2 nanoparticles and bulk silicon. The energy band diagram of hybrid Au@PbI2 nanocomposite under illumination condition prepared at 100 laser pulses was constructed.

High performance MoO3−x/Si heterojunction photodetectors with nanoporous pyramid Si arrays for visible light communication application

Self-powered, fast-response heterojunction photodetectors based on nanoporous pyramid Si arrays are successfully developed. The photodetector is further integrated into a visible light communication system as an optical signal receiver.

Effects of Different Oxidation Degrees of Graphene Oxide on P-Type and N-Type Si Heterojunction Photodetectors.

Oxygen-containing functional groups in graphene oxide (GO), a derivative of graphene, can widen the bandgap of graphene. In this study, we varied the amount of hydrogen peroxide used to prepare GO samples with different degrees of oxidation. Transmittance measurement, Raman spectroscopy, and X-ray photoelectron spectroscopy were used to completely characterize the change in oxidation degree. The effects of oxidation degree on p-type and n-type Si heterojunction photodetectors were compared. Notably, GO with a lower oxidation degree led to a larger photoresponse of p-type Si, whereas that with a higher oxidation degree achieved a larger photoresponse of n-type Si.

Metal-induced growth of crystal Si for low-cost Al:ZnO/Si heterojunction thin film photodetectors

Quality crystal silicon (Si) thin films were grown via the metal-induced growth (MIG) method, which is a low-cost and metal-silicide assisted technique. The metal catalysts of Ni, Pd and Co were first deposited onto substrates for silicide template layer formation. Then, crystal Si thin films with a thickness of ~ 5 µm were epitaxially deposited on the silicide seeds via DC magnetron sputtering. The crystallinity of the Si films was confirmed and investigated by X-ray diffraction (XRD). These Si thin films were then used to fabricate Al doped ZnO (AZO)/MIG Si heterojunction photodetectors. The device achieved a saturation photocurrent of 23.2 mA/cm2 at − 5 V. This photocurrent level is comparable with that of previous reported AZO/bulk-Si devices. Current transport mechanisms and defect distributions were also studied. By analyzing the dark current-voltage (I – V) characteristics, the space charge limited (SCL) current dominated junction behaviors with an exponential defect level distribution were determined. In the bias range of 0.25 V < V < 1.0 V, SCL current transported in the mobility regime based on I ∝ Vβ, where β > 3. For 0 < V < 0.25 V, tunneling and SCL current in ballistic regime were implied due to I ∝ V1.5. In the reverse bias, the device exhibited SCL current in saturation regime or tunneling, suggested by the unity I-V relation. The fabricated devices with the theoretical understanding of the defect and carrier transport mechanisms provided new design insights for low-cost ZnO/MIG-Si thin film optoelectronics.

Large Area Self-Powered Al-ZnO/(n)Si Hetero-Junction Photodetectors With High Responsivity

Al-ZnO/Si heterojunction-based large area, self-powered, low reverse leakage current, and broadband photodetectors with high responsivity are fabricated using the simple and low temperature process. Different from widely applied (p)Si-based heterojunctions, these devices are (n)Si-based and offer superior performance. With optimized Al–ZnO thickness, excellent light confinement is achieved. An interfacial passivation layer that improves the hetero-interface helps achieved a reverse current density as low as $4.5 \times 10^{-7}$ A/cm $^{-2}$ at −0.5 V for a 4.84 cm2 device, with rectification ratio of $2.7 \times 10^{3}$ at ±0.5 V. In self-powered mode, the photodetector achieved responsivities of 0.292, 0.426, and 0.486 A/W (external quantum efficiency, EQE of 78.7%, 96.1%, and 98.8%) for primary blue (460 nm), green (550 nm), and red (610 nm) light, respectively. The operation of self-powered Al–ZnO/(n)Si photodetectors is demonstrated for the first time with modulated optical signal at circuit level.

The light-induced pyro-phototronic effect improving a ZnO/NiO/Si heterojunction photodetector for selectively detecting ultraviolet or visible illumination.

In this work, we fabricate a ZnO/NiO/Si heterojunction photodetector, which successfully realizes selective detection of UV or visible light in a single photodetector. In addition, the pyro-phototronic effect has been confirmed as an effective approach for enhancing the performance of photodetectors based on ZnO. The pyro-phototronic effect is carefully studied by comparing with a ZnO/Si heterojunction photodetector under UV and visible illumination at different bias voltages. To enhance the photodetector's wavelength selectivity, the parameters and structure are further optimized for the ZnO/NiO/SiO2/Si heterojunction photodetector. The newly designed photodetector may be used to selectively detect and distinguish UV and visible illumination in a single photodetector.

ANNEALING TIME EFFECT ON NANOSTRUCTURED n-ZnO/p-Si HETEROJUNCTION PHOTODETECTOR PERFORMANCE

In this work, n- ZnO /p- Si heterojunction photodetectors were prepared by drop casting of ZnO nanoparticles (NPs) on single crystal p-type silicon substrates, followed by (15–60) min; step-annealing at 600∘C. Structural, electrical, and optical properties of the ZnO NPs films deposited on quartz substrates were studied as a function of annealing time. X-ray diffraction studies showed a polycrystalline, hexagonal wurtizte nanostructured ZnO with preferential orientation along the (100) plane. Atomic force microscopy measurements showed an average ZnO grain size within the range of 75.9 nm–99.9 nm with a corresponding root mean square (RMS) surface roughness between 0.51 nm–2.16 nm. Dark and under illumination current–voltage (I–V) characteristics of the n- ZnO /p- Si heterojunction photodetectors showed an improving rectification ratio and a decreasing saturation current at longer annealing time with an ideality factor of 3 obtained at 60 min annealing time. Capacitance–voltage (C–V) characteristics of heterojunctions were investigated in order to estimate the built-in-voltage and junction type. The photodetectors, fabricated at optimum annealing time, exhibited good linearity characteristics. Maximum sensitivity was obtained when ZnO / Si heterojunctions were annealed at 60 min. Two peaks of response, located at 650 nm and 850 nm, were observed with sensitivities of 0.12–0.19 A/W and 0.18–0.39 A/W, respectively. Detectivity of the photodetectors as function of annealing time was estimated.

Using aluminum-induced polycrystalline silicon to enhance ultraviolet to visible rejection ratio of ZnO/Si heterojunction photodetectors

Zinc oxide (ZnO) was deposited on aluminum-induced polycrystalline silicon (AIC-pc-Si) thin film, instead of on a conventional bulk silicon (Si) substrate, and n-ZnO/p-AIC-pc-Si heterojunction photodetectors (HPDs) were fabricated. It is found that the usage of AIC-pc-Si film can largely reduce the visible response by nearly 3 orders of magnitude compared to the conventional Si substrate, making the HPDs practical for real ultraviolet (UV) detection. The drastically reduced visible response achieves a much higher UV (340nm)/visible (500nm) rejection ratio of 2.1×103 than that (7.82) in conventional ZnO/p-Si substrate HPDs. Two major contributions are responsible for the drastic reduction in visible response. One is the very thin (300nm) AIC-pc-Si film, which is much thinner than the bulk Si substrate (about 600μm); the very thin AIC-pc-Si film absorbs very few visible photons and hence lowers visible response. Another issue is the addition of Al atom. During the deposition of ZnO, Al atoms diffuse from the AIC-pc-Si film and build up a bump between the ZnO and AIC-pc-Si. The addition of Al in ZnO increases the electron concentration of ZnO, creating a new structure of n-ZnO/n+-ZnO/AIC-pc-Si. The corresponding band diagram shows a hollow region exists in the n+-ZnO, where the visible-light-generating electrons are recombined by the defect states at n-ZnO/AIC-pc-Si interface, largely suppressing the visible response.