Metal-semiconductor-metal UV Photodetector Research Articles

Enhanced Performance of Metal‐Semiconductor‐Metal UV Photodetectors on Algan/Gan Hemt Structure via Periodic Nanohole Patterning

AbstractAlGaN/GaN High Electron Mobility Transistor (HEMT) structures offer superior electrical and material properties that make them ideal for the fabrication of high‐performance Ultraviolet photodetectors (UV PDs), especially using the metal‐semiconductor‐metal (MSM) configuration. However, the metal layout of the MSM design and crystal defects in multi‐stack HEMTs can reduce photocurrent and degrade device performance. Nano‐structuring of the AlGaN/GaN surface with different nanofeatures is a promising approach to improve light absorption efficiency and increase device response. In this work, AlGaN/GaN HEMT MSM UV photodetectors with enhanced performance parameters by engineering the surface with periodic nanohole arrays are demonstrated. Optical simulations are used to optimize the design of the nanoholes' periodicity and depth. Unpatterned and nanohole‐patterned devices with varying nanohole depths are fabricated, and their performance shows substantial enhancement with the incorporation of nanoholes. The device with 40 nm deep nanoholes and 230 nm array periodicity shows the highest performance in terms of photocurrent (0.15 mA), responsivity (1.4 × 105 A W−1), UV/visible rejection ratio (≈103), and specific detectivity (4.9 × 1014 Jones). These findings present a HEMT‐compatible strategy to enhance UV photodetector performance for power optoelectronic applications, highlighting that nanohole patterning is a promising prospect for advancements in UV photodetection technology.

Realization of a Self-Powered InGaZnO MSM UV Photodetector Using Localized Surface Fluorine Plasma Treatment

Metal–semiconductor–metal (MSM) photodetectors (PDs) are used for optoelectronic integrated circuits (OEICs) because they allow easy integration with a pre-existing circuit. However, traditional MS...

Post-deposition annealed MoO3 film based high performance MSM UV photodetector fabricated on Si (100)

Molybdenum oxide (MoO3) films were prepared on Si (100) at room temperature using radiofrequency (RF) magnetron sputtering technique. The films were annealed in the presence of air at different temperatures from 100 to 550 °C. The as-prepared films were amorphous as revealed by the X-ray diffraction analysis. Post-deposition annealing of MoO3 film enhanced its crystalline structure, showing β-MoO3 phase at 100 °C and a mixture of α-MoO3 and β-MoO3 phases at 300 °C. The crystallinity of α-MoO3 improved with increasing the annealing temperature to 500 °C, however, the β-MoO3 phase became amorphous. The film was dissolved at 550 °C as no diffraction peak of MoO3 was detected at this temperature. The band gap of MoO3 was evaluated through ultraviolet–visible spectroscopy. The results showed a decrease in the band gap from 3.70 to 3.39 eV with increasing the annealing temperature to 500 °C. The film with optimum crystalline quality was used to fabricate a metal-semiconductor-metal (MSM) photodetector device. The photo-detection characteristics of the film were studied after the deposition of Nickel contacts on MoO3 using a metal mask having interdigitated electrodes. The fabricated device exhibited a high current gain and sensitivity under 365 nm UV illumination. The responsivity of the device under UV light was 0.41 A/W at 7 V. The rise and decay time of UV photodetector were 0.32 and 0.23 s respectively. These findings suggested that the MoO3 film with dominant orthorhombic α-phase can potentially be used for the photodetector application.

An optimized Graphene/4H-SiC/Graphene MSM UV-photodetector operating in a wide range of temperature

In this paper,. an accurate analytical model has been developed to optimize the performance of an Interdigitated Graphene Electrode/p-silicon carbide (IGE/p-4H-SiC) Metal semiconductor Metal (MSM) photodetector operating in a wide range of temperatures. The proposed model considers different carrier loss mechanisms and can reproduce the experimental results well. An overall assessment of the electrodes geometrical parameters’ influence on the device sensitivity and speed performances was executed. Our results confirm the excellent ability of the suggested Graphene electrode system to decrease the unwanted shadowing effect. A responsivity of 238 μA/W was obtained under 325-nm illumination compared to the 16.7 μA/W for the conventional Cr-Pd/p-SiC PD. A photocurrent to- dark-current ratio (PDCR) of 5.75 × 105 at 300 K and 270 at 500 K was distinguished. The response time was found to be around 14 μs at 300 K and 54.5 μs at 500 K. Furthermore, the developed model serves as a fitness function for the multi objective optimization (MOGA) approach. The optimized IGE/p-4H-SiC MSM-PD design not only exhibits higher performance in terms of PDCR (7.2 × 105), responsivity (430A/cm2) and detectivity (1.3 × 1014 Jones) but also balances the compromise between ultrasensitive and high-speed figures of merit with a response time of 4.7 μs. Therefore, the proposed methodology permits to realize ultra-sensitive, high-speed SiC optoelectronic devices for extremely high temperature applications.

Hydrothermally-Grown TiO2 Thin Film-Based Metal–Semiconductor–Metal UV Photodetector

A metal–semiconductor–metal (MSM) ultraviolet photodetector has been fabricated by using hydrothermally-grown TiO2 thin films. Ag paint was used as a contact electrode which showed the good ohmic contact between the metal–semiconductor junctions. The effect of deposition time on the structural, morphological and photodetector properties have been studied. The prepared TiO2 thin films are polycrystalline and show a rutile crystal structure with the preferred orientation along the (110) plane. The MSM UV photodetector was illuminated under a UV lamp with an intensity of 1.8 μW/cm2 and at 5-V bias. The photocurrent of the device increased linearly with the applied voltage. The maximum photocurrent of 3.96 μA was obtained for the film deposited at 5 h and maximum spectral photoresponsivity was 13.29 A/W. The device showed a fast optical switching behavior. The high responsivity and fast photoresponse shows that fabricated TiO2 detectors are good candidates for ultraviolet photodetectors.

The Effect of Oxygen Partial Pressure and Annealing Process on the Characteristics of ZnGa2O4 MSM UV Photodetector

In this work, ZnGa2O4 solar-blind photodetectors (PD) based on a metal-semiconductor-metal (MSM) structure was fabricated by radio frequency (RF) magnetron sputtering method. The transmittance of the material shows larger than 80% cross the visible light region. As a wide bandgap and high transparency semiconducting material, ZGO is a potential candidate for UV-detection applications. The ZGO MSM PD with no oxygen flow during sputtering exhibits a responsivity of 4.46 × 10−2 A/W under illumination at wavelength of 260 nm, rejection ratio of 1.75 × 104. The performance can be enhanced with proper thermal annealing process. With an annealing process at temperature of 200°C, the responsivity and rejection ratio are 0.203 A/W and 1.12 × 105, respectively.

Self-powered ZnS Nanotubes/Ag Nanowires MSM UV Photodetector with High On/Off Ratio and Fast Response Speed

In this study, we design and demonstrate a novel type of self-powered UV photodetectors (PDs) using single-crystalline ZnS nanotubes (NTs) as the photodetecting layer and Ag nanowires (NWs) network as transparent electrodes. The self-powered UV PDs with asymmetric metal-semiconductor-metal (MSM) structure exhibit attractive photovoltaic characteristic at 0 V bias. Device performance analysis reveals that the as-assembled PDs have a high on/off ratio of 19173 and a fast response speed (τr = 0.09 s, τf = 0.07 s) without any external bias. These values are even higher than that of ZnS nanostructures- and ZnS heterostructure-based PDs at a large bias voltage. Besides, its UV sensivity, responsivity and detectivity at self-powered mode can reach as high as 19172, 2.56 A/W and 1.67 × 1010 cm Hz1/2 W−1, respectively. In addition, the photosensing performance of the self-powered UV PDs is studied in different ambient conditions (e.g., in air and vacuum). Moreover, a physical model based on band energy theory is proposed to explain the origin of the self-driven photoresponse characteristic in our device. The totality of the above study signifies that the present self-powered ZnS NTs-based UV nano-photodetector may have promising application in future self-powered optoelectronic devices and integrated systems.

Fabrication and characterization of high performance MSM UV photodetector based on NiO film

In this study, metal-semiconductor-metal (MSM) ultraviolet photodetector based on NiO film was fabricated on n-type Si (100) substrate. The NiO film was deposited on Si (100) by using RF magnetron sputtering of NiO target at 100°C. The film showed cubic bunsenite structure with (200) preferred orientation as confirmed through XRD analysis. The band gap of NiO film was evaluated from UV–vis reflectance specroscopy and it was found to be 3.38eV. To study the photodetection performance of NiO film, Au metal contacts were deposited on the film through RF sputtering system. The photodetection characteristics of the photodetector such as spectral response, photosensivity, internal gain, rise and fall time were investigated. The Au/NiO/Au MSM UV device displayed maximum value of responsivity (4.5A/W) upon exposure to 365nm UV light at 5V bias. The photosensivity was calculated to be 6.4×103% whereas the internal gain of the photodetector was estimated to be 6.5×101. In addition, the rising and falling time were found to be 266ms and 200ms, respectively. The fabricated device exhibited excellent stability and repeatability in its performance.

Growth of AlInN film on GaAs substrate and its application to MSM UV photodetector

AlInN film was grown on n-type GaAs (100) substrate by using reactive magnetron co-sputtering technique at 100 °C. The structural analysis revealed polycrystalline nature of the film with its preferred orientation along (002) plane. The band gap of AlInN was estimated to be 3.39 eV from UV–vis reflectance measurements. In order to fabricate AlInN based metal–semiconductor–metal (MSM) photodetector, platinum (Pt) metal contacts were deposited on the film through RF sputtering. The Pt/AlInN/Pt/GaAs MSM photodetector displayed good responsivity under 365 nm UV light. The current–voltage characteristics of the fabricated photodetector showed significant increase in current upon exposure to 365 nm UV light. The current gain for the MSM photodetector under 365 nm UV light at 5 V bias was recorded to be 29.4 whereas the sensitivity of the photodetector was noted to be 2.9 × 103. The response and recovery time were estimated to be 0.70 and 0.72 s respectively. The fabricated device exhibited excellent stability in ON/OFF switching conditions.

Physical and UV photodetection properties of pulsed laser deposited Mg0.05Zn0.95O thin films: Effect of oxygen pressure

Mg0.05Zn0.95O (or MZO) thin films have been deposited onto glass substrates by pulsed laser deposition (PLD) at 400°C under various oxygen pressures. All the films exhibit the wurtzite phase with a preferential c-axis orientation. The compact packing of the crystal grains is observed for the MZO films prepared at lower oxygen pressure. The grain size, film thickness and surface roughness are observed to be reduced with increasing oxygen pressure. The optical transmittance increases with an increase in oxygen pressure and the band gap experiences a red shift. The room temperature UV photodetection properties of MZO films were investigated in metal–semiconductor–metal (MSM) planar configurations and are found to be highly dependent on oxygen pressure. The photocurrent improves on reduction in the oxygen pressure due to enhancement in film crystallinity and oxygen vacancies. The photocurrent and responsivity were measured as a function of optical power density and applied voltage, respectively. The stability of MSM UV photodetectors was ensured by periodically switching the photoillumination on and off at regular time intervals. Highly stable and fast switching UV photoresponse characteristics are confirmed for the photodetector having MZO film prepared at 2×10−3torr oxygen pressure; which demonstrates highest responsivity of ∼0.2275A/W upon 2mW/cm2 UV exposures at 365nm at 5V bias voltages.

AlxGa1−xN/GaN/AlN heterostructures grown on Si(1 1 1) substrates by MBE for MSM UV photodetector applications

AlxGa1−xN/GaN/AlN heterostructures on silicon (Si) substrate was developed by nitrogen plasma-assisted molecular beam epitaxy (MBE) and their properties were investigated by scanning electron microscopy (SEM), electron dispersive X-ray (EDX), atomic force microscopy (AFM), high resolution X-ray diffraction (XRD), Raman spectroscopy and Hall effect measurements. High purity gallium (7N) and aluminum (6N5) were used in the Knudsen cells. High purity nitrogen with 7N purity was supplied to radio frequency (RF) source to generate reactive nitrogen species. The nitrogen pressure and a discharge power were kept at 1.5×10−5Torr and 300W, respectively. From SEM measurements, the surface morphology of samples presented 2- and 3-dimensional growth modes. The EDX measurements showed that there were no foreign elements in the grown samples. The HR-XRD measurement has confirmed that the AlxGa1−xN/GaN/AlN heterostructures samples were epitaxially grown on Si substrate. All the dominant E2 phonon modes were found in Raman spectra results. Lastly, AlxGa1−xN/GaN/AlN heterostructures based metal–semiconductor–metal (MSM) UV photodetectors were fabricated and the electrical characteristics of the devices were investigated by using current–voltage (I–V) and photo-conductivity measurements. The devices presented good I–V and photoconductivity characteristics.

AlN/GaN/AlN heterostructures grown on Si substrate by plasma-assisted MBE for MSM UV photodetector applications

The AlN/GaN/AlN heterostructures were successfully grown on silicon substrate by plasma-assisted molecular beam epitaxy (MBE). High purity gallium (7N) and aluminum (6N5) were used to grow GaN and AlN, respectively. The structural and optical properties of the samples have been investigated by high-resolution X-ray diffraction (HR-XRD), photoluminescence (PL), Raman spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction (SAED), dark field scanning transmission electron microscopy (DF STEM), and high-angle annular dark field scanning transmission electron microscopy (HAADF STEM). HR-XRD measurement showed that the sample has a typical diffraction pattern of hexagonal AlN/GaN/AlN heterostructures. Raman spectra revealed all four Raman-active modes, i.e., GaN-like E2 (H), AlN-like A1 (TO), AlN-like E2 (H), and AlN-like A1 (LO) inside the AlN/GaN/AlN heterostructures. Good thickness uniformity of the layers and high-quality hetero-structures without cracking were confirmed by TEM, SAED, DF STEM and HAADF STEM. The fabricated AlN/GaN/AlN heterostructures based metal-semiconductor-metal (MSM) for the UV photodetector shows a rise and fall of photoresponses, suggesting that the AlN/GaN/AlN heterostructures have good carrier transport and crystallinity properties.

High-performance metal–semiconductor–metal UV photodetector based on spray deposited ZnO thin films

Zinc oxide (ZnO) based metal–semiconductor–metal (MSM) ultraviolet photodetectors at different substrate temperatures were fabricated on glass substrates by economical chemical spray pyrolysis technique and its UV photoresponsivity was measured at room temperature. The samples were characterized with respect to their structural, morphological, and optical properties using various methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–Vis spectroscopy, transmittance, reflectance etc. The synthesized ZnO thin films were c-axis oriented with hexagonal crystal structure as confirmed from XRD. All deposited films were specular and show high transmittance (∼85%) in visible region with steep fall off at 375nm. The photoconductive MSM UV photodetector showed relatively high photocurrent (1.3mA) and fast switching. ZnO thin films exhibited relatively high photoresponsivity (788A/W) with cut of wavelength ∼375nm signifying their application as UV detector.

Electrical and optical effects of Pd microplates embedded in ZnO thin film based MSM UV photodetectors: A comparative study

This paper reports the characterization of ZnO-based interdigitated metal–semiconductor–metal (MSM) Schottky barrier UV photodetectors fabricated by three methods. Specifically, devices having Pd Schottky contacts based on un-doped ZnO, Pd doped ZnO and Pd microplates embedded ZnO films. All ZnO films were grown on p-type Si 〈111〉 substrates by the sol–gel method. For embedded devices, Pd microplates where first grown on the substrate by thermal evaporation using a 80μm mesh shadow mask. We have estimated the photocurrent, contrast ratio, responsivity, and quantum efficiency of the photodetectors for applied voltage from −5 to 5V and optical power from 50 to 200μW at 365nm. The current–voltage characteristics were studied and parameters such as ideality factor, leakage current, and barrier height of the Schottky contacts were extracted. The barrier height dependence on the electric field and tunneling through the barrier has been taken into account of the studied MSM devices. The bandgap of both undoped ZnO and ZnO:Pd are evaluated from the absorbance spectra via double beam spectrophotometry. Surface morphology of the ZnO films was studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM). All devices showed a maximum photo-response at flat band voltages of MSMs. It was found that there is no significant difference between un-doped and Pd doped ZnO derived devices performance. The study also revealed that the Pd microplates embedded ZnO films resulted in devices exhibiting better photoresponse as compared to those using un-doped ZnO and ZnO:Pd thin films.

Growth of GaN films on silicon (1 1 1) by thermal vapor deposition method: Optical functions and MSM UV photodetector applications

In this study, gallium nitride (GaN) films were grown on n-Si (111) substrate by thermal vapor deposition method in quartz tube furnace for different growth duration. Gallium metal mixed with GaN powder and aqueous ammonia (NH3) solutions were used as sources of Ga and N. Structural, elemental, and optical characterizations were carried out using various techniques in order to investigate the properties of the films. Scanning electron microscopy images showed that the films surface have self-textured morphology, which was introduced during the growth process. Moreover, further deposition resulted in the formation of heterogeneous film. X-ray diffraction (XRD) measurements reveal in all samples a typical diffraction pattern of hexagonal GaN wurtzite structure. Raman spectra demonstrated redshifts in E2-high with increasing deposition time due to tensile stress inside the GaN films, confirmed by XRD. The photoluminescence spectra of the films demonstrated strong near band edge emission at about 363nm. The fabricated GaN films based metal–semiconductor-metal (MSM) UV photodetector shows a contrast ratio of ∼240–40 at +5V and responsivity in the range of 0.28–0.01A/W for the UV photodetectors. This study shows the possibility of synthesizing GaN films on Si wafers at low-cost and has potential applications in UV photodetection.

Porous-shaped silicon carbide ultraviolet photodetectors on porous silicon substrates

A metal–semiconductor-metal (MSM) ultraviolet photodetector was fabricated based on a porous-shaped structure of silicon carbide (SiC). For increasing the surface roughness of SiC and hence enhancing the light absorption effect in fabricated devices, porous silicon (PS) was chosen as a template; SiC was deposited on PS substrates via radio frequency magnetron sputtering. Therefore, the deposited layers followed the structural pattern of PS skeleton and formed a porous-shaped SiC layer on PS substrate. The structural properties of samples showed that the as-deposited SiC was amorphous. Thus, a post-deposition annealing process with elevated temperatures was required to convert its amorphous phase to crystalline phase. The morphology of the sputtered samples was examined via scanning electron and atomic force microscopies. The grain size and roughness of the deposited layers clearly increased upon an increase in the annealing temperature. The optical properties of sputtered SiC were enhanced due to applying high temperatures. The most intense photoluminescence peak was observed for the sample with 1200°C of annealing temperature. For the metallization of the SiC substrates to fabricate MSM photodetectors, two interdigitated Schottky contacts of Ni with four fingers for each electrode were deposited onto all the porous substrates. The optoelectronic characteristics of MSM UV photodetectors with porous-shaped SiC substrates were studied in the dark and under UV illumination. The electrical characteristics of fabricated photodetectors on annealed substrates showed enhanced sensitivity and responsivity to ultraviolet radiation.

A Theoretical and Experimental Comparison of 4H- and 6H-SiC MSM UV Photodetectors

This paper reports on fabrication and modeling of 4H- and 6H-SiC metal-semiconductor-metal (MSM) photodetectors (PDs). MSM PDs have been fabricated on 4H-SiC and 6H-SiC epitaxial layers, and their performance analyzed by MEDICI simulation and measurements. The simulations were also used to optimize the sensitivity by varying the width and spacing of the interdigitated electrodes. The fabricated PDs with 2 µm wide metal electrodes and 3 µm spacing between the electrodes exhibited, under UV illumination, a peak current to dark current ratio of 105 and 104 in 4H-SiC and 6H-SiC, respectively. The measured spectral responsivity of 6H-SiC PDs was higher compared to that of 4H-SiC PDs, with a cutoff at 407 nm compared to 384 nm in 4H-SiC PDs. Also the peak responsivity occurred at a shorter wavelength in 6H material. A high rejection ratio between the photocurrent and dark current was found in both cases. These experimental results were in agreement with simulation.

Effect of AlN film thickness on photo/dark currents of MSM UV photodetector

AbstractIn this article, we have successfully fabricated the metal‐semi‐conductor‐metal (MSM) UV photodetector using the aluminum nitride‐based (AlN) film as an active layer grown on p‐type Si (100) by a dc sputtering deposition. Effect of AlN thickness of 500, 1500, and 2500 nm on the surface morphology of the AlN film and photo/dark currents of the MSM photodetector is investigated. With increase of the AlN thickness, XRD result shows the crystallization of AlN film increases. The device can be extensively used in solar‐blind UV applications. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2863–2866, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23796

High detectivity GaN metal–semiconductor–metal UV photodetectors with transparent tungsten electrodes

GaN metal–semiconductor–metal (MSM) ultraviolet photodetectors with transparent tungsten (W) electrodes were fabricated and characterized. It was found that the 10 nm thick W film deposited with a 250 W RF power could provide a reasonably high transmittance of 68.3% at 360 nm, a low resistivity of 1.5 × 10−3 Ω cm and an effective Schottky barrier height of 0.777 eV on u-GaN. We also achieved a peak responsivity of 0.15 A W−1 and a quantum efficiency of 51.8% at 360 nm from the GaN MSM UV photodetector with W electrodes. With a 2 V applied bias, it was found that the minimum noise equivalent power (NEP) and the maximum D* of our detector were 1.745 × 10−10 W and 7.245 × 109 cm Hz0.5 W−1, respectively.

Nitride-based MSM UV photodetectors with photo-chemical annealing Schottky contacts

The undoped GaN (u-GaN) and two-dimensional electron gas (2DEG) metal–semiconductor–metal (MSM) photodetectors with semi-transparent Ni/Au Schottky barrier contact electrodes were fabricated. It was found that we could achieve a larger Ni/Au transmittance, higher Schottky barrier heights and larger photocurrent to dark current contrast ratios by photo-chemical annealing of these photodetectors in O 2. It was also found that the maximum quantum efficiencies were 13% and 57% for the photo-chemical annealing u-GaN and 2DEG photodetectors, respectively. Furthermore, it was found that we could achieve a larger responsivity, a lower noise level and a larger detectivity by using the 2DEG structure.