Transistor Photodetector Research Articles

Performance Analysis of a 4H-SiC n-p-n Phototransistor With Floating Base for Ultraviolet Light Detection

A 4H-SiC n-p-n bipolar phototransistor detector (PTD) with a floating-base configuration is fabricated and studied in this work. The PTD exhibits low dark current and high responsivity in the ultraviolet (UV) wavelength band, which results in a large photo-to-dark current ratio (PDCR). The optical gain of the PTD is found highly dependent on the incident light intensity, which is larger at high light levels. Nevertheless, at low light levels, a unity gain is obtained, which is limited by the recombination current within the emitter–base (E–B) junction. The PTD further exhibits high-temperature operation potential and a detectivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7.06\times 10^{{12}}$ </tex-math></inline-formula> cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> Hz <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\text {1/2}}$ </tex-math></inline-formula> /W can be achieved at 150 °C. The transient response characteristics of the PTD are characterized as a function of incident power density and temperatures. It is found that optical gain and junction capacitance are both important for explaining the variation trends of response time. Finally, a demonstration board is designed and fabricated to test the potential of the SiC PTD for UV radiometer applications. When operating in active mode, the PTD circuit could exhibit reasonable linear response to incident UV power density.

High-Temperature Performance of the 4H-SiC n-p-n Bipolar UV Phototransistor

Excellent high-temperature performance (298–523 K) of the 4H-SiC n-p-n bipolar phototransistor detector (PTD) was explored. It was fabricated using the 4H-SiC epitaxial wafer grown by high-temperature chemical vapor deposition (HTCVD). The static and dynamic properties of the device were tested and analyzed. The results show that the device still has an optical gain of up to 103, a wide linear response range, and good repeatability at the high temperatures up to 523 K under a 3-V bias with a wavelength of 360 nm. The temperature coefficient of the optical gain is extracted, the value of which is 1.02/K. Although the response time of the device increases with the temperature, the increased percentage in responsivity is significantly greater than that of the response time. The results provide an important experimental reference for the application of high-temperature detection and suggest that the PTD has the potential to be used in ultraviolet (UV) detecting systems at high temperatures.

Low-Voltage and High-Gain Ultraviolet Detector Based on 4H-SiC n-p-n Bipolar Phototransistor

A two-terminal 4H-SiC n-p-n bipolar phototransistor detector (PTD) with high gain is demonstrated. It was fabricated using the 4H-SiC epitaxial wafer grown by high-temperature chemical vapor deposition. The PTD shows a large photocurrent and responsivity enhancement over the conventional 4H-SiC p-i-n photodetector (PD). These enhancement effects are owing to the internal gain of the bipolar transistor. The detector shows a high optical gain of ~ 1450 at 360 nm and has a linear response to the ultraviolet (UV) light in the wide light intensity range of 0.7– $700~\boldsymbol \mu \text{W}\boldsymbol /$ cm2 at a low operating voltage of 3 V. The PTD can respond to the UV light from 220 to 340 nm and the peak responsivity is $\sim 125~\text{A}\boldsymbol /\text{W}$ at 275 nm. This work is significant for developing high-performance SiC-based bipolar phototransistors.

In₂Se₃/Silicon-on-Insulator Heterojunction Phototransistor for Low Noise Dual-Band Detection

In this study, high-performance In2Se3/Silicon-on-Insulator (SOI) heterojunction field-effect transistor photodetector is fabricated. The In2Se3/Si heterostructure phototransistor exhibits dual-band detection with a maximum responsivity of 12 A/W and 41 A/W for illumination of 405 nm and 800 nm wavelengths, respectively. This phototransistor has shown a lower noise-equivalent power of 6.8 fW.Hz $^{-1/2}$ and higher detectivity of $2.9\times 10^{13}$ cm.Hz $^{1/2}\text{W}^{-1}$ . Flicker noise dominates the In2Se3/SOI phototransistor with a corner frequency of 3 Hz. The device’s enhanced performance is due to the improved synergistic effect with efficient electron-hole dissociation in the heterojunction. This heterostructure based photodetector can be of great interest for dual-band (Ultra-violet and visible) detection in imaging, optical communication and healthcare applications.

Substrate effects in graphene field-effect transistor photodetectors

In present study, we introduce graphene field-effect transistors (G-FET) fabricated on silicon - silicon dioxide wafers and analyse their properties. Electric and photoelectric effects in these devices were experimentally observed and discussed. We demonstrate that the understanding of the processes occurring in the substrate is of high importance not only for the development of all types of photodetectors based on field-effect transistors, but also could be used for the designing of devices with novel functionalities.

Field effect transistor photodetector based on two dimensional SnSe&lt;sub&gt;2&lt;/sub&gt;

Two dimensional materials have been attracting intensive interest due to their unique physical and optoelectronic properties. As an emerging two dimensional materials, SnSe&lt;sub&gt;2&lt;/sub&gt; have shown a considerable potential for next-generation electronic and optoelectronic. Herein, SnSe&lt;sub&gt;2&lt;/sub&gt; bulk crystals have been prepared by a chemical vapour transport method with high purity tin and selenium powder as precursors. Then SnSe&lt;sub&gt;2&lt;/sub&gt; multilayers has been successfully prepared by a micromechanical exfoliation method from the SnSe&lt;sub&gt;2&lt;/sub&gt; bulk crystals. The phase structures and elemental composition of the bulk crystal are investigated using an X-Ray diffractometer, an X-ray photoelectrons spectrometer and a Raman spectrometer. And the morphologies are observed using an optical microscope, an atomic force microscope and a transmission electron microscope. The measurement results show that the SnSe&lt;sub&gt;2&lt;/sub&gt; bulks are single crystals with a high crystallization and purity. The SnSe&lt;sub&gt;2&lt;/sub&gt; multilayers have a size of 25–35 μm and a thickness of 1.4 nm. To detect the electronic and photoresponse characteristics of the SnSe&lt;sub&gt;2&lt;/sub&gt; multilayers, a field effect transistor based on such SnSe&lt;sub&gt;2&lt;/sub&gt; are fabricated via a photolithographic-pattern-transfer method. The transistor has a smooth surface without wrinkles and bubbles, and also has a good contact with Au electrodes. The transistor shows a linear output characteristic and an obvious rectification. The on/off ratio of the device is 47.9 and the electron mobility is 0.25 cm&lt;sup&gt;2&lt;/sup&gt;·V&lt;sup&gt;–1&lt;/sup&gt;·s&lt;sup&gt;–1&lt;/sup&gt;. As a photodetector, the field effect transistor exhibits obvious photoresponse to three visible lights with the wavelengths of 405, 532, and 650 nm. As the lasers are turned on and the device is under illuminations of three visible lights, the current increase rapidly to a saturation state. Then as the lasers are switched off, the current decrease and recover to the original state. The drain-source current can alternate between high and low states rapidly and reversibly, which demonstrates photoresponse characteristics of the devices are stable and sensible. Notably, it shows a strongest response to the 405 nm light at an intensity of 5.4 mW/cm&lt;sup&gt;2&lt;/sup&gt; with a high responsivity of 19.83 A/W, a good external quantum efficiency of 6.07 × 10&lt;sup&gt;3&lt;/sup&gt;%, a normalized detectivity of 4.23 × 10&lt;sup&gt;10&lt;/sup&gt; Jones, and a fast response time of 23.8 ms. The results of this work demonstrate that layered SnSe&lt;sub&gt;2&lt;/sub&gt; can be a suitable and excellent candidate for visible light photodetector and has a huge potential for high-performance optoelectronic devices.

Simulation study of ZnO nanowire FET arrays for photosensitivity enhancement of UV photodetectors

An ultraviolet photodetector based on zinc oxide nanowire field effect transistor is designed and simulated in three configurations including single nanowire, three parallel and array of six nanowires. Transient response of photodetectors is studied by mixed-mode simulation. Results demonstrate that the light/dark current ratio is increased to 10 for the parallel and array of six nanowires. Transmission percentage of undesired wavelengths increases to 80% in the array of six nanowires, additionally. Furthermore, parallel nanowires detectors enhance photosensitivity from 3.325 in single nanowire structure to 12.477 in parallel structure; however, it does not impact on quantum efficiency. On the other hand, the array of six nanowires structure raises external quantum efficiency substantially from 50% for single nanowire to 58%. Moreover, array structure stables the photodetector in a variety of illumination angles. Although, field effect transistor photodetector structure improves the performance of UV detector and boost photodetector response time, three parallel and array of six nanowires structures slightly increase response time to 8.4 and 9.9 μs, respectively in comparison with single nanowire structure. The proposed UV detector receives an encouraging response to μW range of power light intensity.

Field effect transistor photodetector based on graphene and perovskite quantum dots

Graphene is an attractive optoelectronic material for various optoelectronic devices, especially in the field of photoelectric detection due to its high carrier mobility and fast response time. However, the relatively low light absorption cross-section and fast electron-hole recombination rate can lead to rapid exciton annihilation and small light gain, which restrict the commercial applications of pure graphene-based photodetector. The perovskite has attracted much attention because of its high photoelectric conversion efficiency in the field of solar cells. The perovskite has the advantages of long carrier diffusion distance and high optical absorption coefficient, which can effectively make up for the shortcomings of pure graphene-based field-effect transistor. In this work, a field-effect transistor photodetector is demonstrated with the combination of graphene and halide perovskite quantum dots (CsPbI3) serving as conductive channel materials. The graphene is prepared by plasma enhanced chemical vapor deposition, and the quantum dots are CsPbI3 perovskite. The electrical properties of graphene and pure graphene-based field-effect transistor are detected and analyzed by using the Raman spectrum. The results show that the graphene has good intrinsic electrical properties. Unlike previous report in which bulk perovskite was used, the perovskite quantum dot field-effect transistor photodetector has an obvious light response to 400 nm signal light, and shows the excellent photoelectrical performance. Under the illumination of 400 nm light, the signal light could be detected steadily and repeatedly by the graphene-perovskite quantum dot photodetector and converted into photocurrent. The photocurrent of the photodetector has a rapid rise, and the maximum value can reach 64 A at a light power of 12 W. The corresponding responsivity is 6.4 AW-1, which is two orders of magnitude higher than that of the general single graphene photodetector (10-2 AW-1), and it is also higher than that of perovskite-based photodetector (0.4 AW-1). In addition, the photoconductive gain and detectivity arrive at 3.7104 and 6107 Jones (1 Jones=1 cmHz1/2W-1), respectively. The results of this study demonstrate that the graphene-perovskite quantum dot photodetector can be a promising candidate for commercial UV light detectors.

Enhancement of photodetection based on perovskite/MoS2 hybrid thin film transistor**Project supported by the National Natural Science Foundation of China (Nos. 11374070, 61327009 214320051) and the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDA09040201).

Perovskite/MoS2 hybrid thin film transistor photodetectors consist of few-layered MoS2 and CH3NH3PbI3 film with various thickness prepared by two-step vacuum deposition. By implementing perovskite CH3NH3PbI3 film onto the MoS2 flake, the perovskite/MoS2 hybrid photodetector exhibited a photoresponsivity of 104 A/W and fast response time of about 40 ms. Improvement of photodetection performance is attributed to the balance between light absorption in the perovskite layer and an effective transfer of photogenerated carriers from perovskite entering the MoS2 channel. This work may provide guidance to develop high-performance hybrid structure optoelectronic devices.

Development of Experimental Set for Determination of Refractive Index of Liquid Using Optical Fiber

The construction of an experimental set for measurement of refractive index of liquids using fiber optics has been described in this work. The experimental set is aimed for demonstration in physics high school class. A prototype fabricated in laboratory composes of plastic-clad-plastic (PCP) optical fiber with the length of 50 cm, fiber optic transmitter diode, fiber optic phototransistor detector, and liquid container. The diameter and refractive index of the core of PCP optical fiber were 1 mm and 1.492, respectively. The thickness and refractive index of fiber cladding were 1.2 mm and 1.417, respectively. The fiber cladding surface at the central region was removed approximately 5 cm long to form a sensor area. This sensor area was inserted into a cylindrical glass which acted as the container. One end of the fiber was connected to the transmitter diode with a wavelength of 660 nm, and the other end was connected to the detector. A digital multimeter was used to measure an output voltage from the detector. In this work, the effect of water temperature on its refractive index was determined. The results showed that the water refractive index decreased with increasing water temperature and result in the increase of measured output voltage. Furthermore, it was found that the output voltage measured at different temperatures of water depends linearly on water refractive index.

Development of a Simple Portable Amylose Content Meter for Rapid Determination of Amylose Content in Milled Rice

For amylose content determination in milled rice, currently, both the preparation method and the equipment used for amylose determination in milled rice are complicated and expensive. The method can only be applied in laboratory and carrying out the test in the field is not suitable. This paper proposes a modified rapid sample preparation procedure and a development of a simple, rapid, and portable device that is applicable for the prediction of the amylose content in rice. The device with a dimension of 170 × 220 × 80 mm and 600 g in weight was designed following the colorimetric method. The portable amylose content meter (PAC meter) consisted of a light source, filter, sample cell (using for input the starch–iodine complex solution as a result of reaction between amylose and iodine), phototransistor detector, and digital multimeter. Phototransistor detector was used for light intensity detection and it could generate current, and voltage was measured by digital multimeter. This device can measure both AC and DC (i.e., 9-V DC battery), allowing the device to be transported. The sample preparation procedure started from ten single kernels of milled rice that were boiled in the boiling water, cooled, and filtered followed by the addition of 0.1 M HCl solution and subsequently stained with iodine–potassium iodide. Next, the amylose–iodine complex was measured using the PAC meter. The regression model was developed based on the measurement of the amylose–iodine complex from the selected five rice varieties and used for the formulation of the standard curve for PAC meter. The regression model equation for the standard curve was established as amylose content (%) = (Absorbance + 0.036)/0.017 (R 2 = 0.99, p < 0.01). The amylose content of the samples was strongly and positively correlated with the absorbance values with 99 % correlation. Furthermore, to study the precision of PAC meter, 11 Thai rice varieties were selected (n = 10). The measurements made using PAC meter showed acceptable precision based on the international measurement system. The accuracy of PAC meter measurements was confirmed by comparing the results with those obtained by the conventional method, which was not significantly different (p < 0.05).The PAC meter is, therefore, applicable in the prediction of amylose content in rice, is of economical price, rapid, straightforward, portable, and reliable. In addition, this development can decrease the analysis period of over 24 h to less than 1 h.

Detecting Infrared Radiation with a Phototransistor and an IR Filter

This paper presents experiments to detect infrared radiation (IR).1 The key materials, which are readily available, are the following: » A phototransistor detector, whose circuit diagram is shown in Fig. 1. The response of the phototransistor, which extends into the near infrared, is shown in Fig. 2, along with the response of the human eye. » An inexpensive infrared filter2,3 — a piece of unexposed, processed Ektachrome® film, which absorbs visible light but transmits infrared.

Single photoelectron trapping, storage, and detection in a field effect transistor

A single photoelectron can be trapped and its photoelectric charge detected by a source/drain channel in a transistor. Such a transistor photodetector can be useful for flagging the safe arrival of a photon in a quantum repeater. The electron trap can be photo-ionized and repeatedly reset for the arrival of successive individual photons. This single photoelectron transistor (SPT) operating at the lambda = 1.3 mu m tele-communication band, was demonstrated by using a windowed-gate double-quantum-well InGaAs/InAlAs/InP heterostructure that was designed to provide near-zero electron g-factor. The g-factor engineering allows selection rules that would convert a photon's polarization to an electron spin polarization. The safe arrival of the photo-electric charge would trigger the commencement of the teleportation algorithm.

Electrical characterisation of a heterojunction field effect transistor photodetector (HFETPD)

An analytic model is developed to determine the gate-substrate potential profile in a heterojunction field-effect transistor photodetector HFETPD. The potential profiles and the associated depletion widths determined by the model are shown to be in excellent agreement with a device simulator which numerically solves the drift-diffusion equations. The behaviour of the active layer depletion width is also studied as a function of gate bias and doping levels in the delta plane, the active layer and barrier layer.

An optical waveguide acid vapor sensor

An optical waveguide sensor for the detection of acid vapors is described. The chemically sensitive reagent coating consists of bromothymol blue indicator suspended in a Nafion polymer film. The sensor uses a 562 nm LED source and a phototransistor detector. Response to hydrochloric acid and hydrogen sulphide vapours is both rapid and reversible, with an estimated detection limit for hydrogen sulphide of less than 15 ppm. The sensors exhibits generalized response to protonic acid vapours, but does not produce an indicator response to carbon dioxide, even at large concentrations (1100 mg/l.) in the presence of water vapor. The sensor exhibits a systematic interference from water vapor which may be corrected by a different approach, either using a reference sensor (Nafion/no indicator) or by monitoring sensor response at two wavelengths.

60 GHz sources using optically driven heterojunction bipolar transistors

Millimeter wave sources at 60 GHz have been demonstrated using optically driven heterojunction bipolar transistors configured as photodetectors. Two techniques were used to optically generate the millimeter waves; the mixing of two cw lasers and the mode locking of a semiconductor laser. The millimeter wave power generated from these two configurations was radiated into free space using integrated planar twin-dipole antennas and heterodyne detected with signal-to-noise ratios ≳40 dB. As part of these experiments, the dc optical gains and quantum efficiencies of the heterojunction bipolar transistor photodetectors were determined.

High-speed integrated heterojunction field-effect transistor photodetector: A gated photodetector

A new concept for a high-speed photodetector is described which promises very low noise with avalanche gain. The detector is constructed as an integrated circuit element in the heterojunction field-effect transistor technology and utilizes a unique n-n heterojunction interface formed by either metalorganic chemical vapor deposition or molecular beam epitaxy growth techniques. The degree of avalanching is controlled via an electrical third terminal.

Simultaneous detection of alkylselenide, alkyllead and alkyltin compounds by gas chromatography using a multi-channel non-dispersive atomic fluorescence spectrometric detector and a miniature flame as the atomiser

A multi-channel non-dispersive atomic fluorescence spectrometer with a miniature argon-hydrogen flame as the atomiser was interfaced with a gas chromatograph using a wide-bore capillary column. The system was tested for the simultaneous detection of alkylselenides (M2Se and Me2Se2), alkylleads (PbMe4 and PbEt4) and alkyltins (SnMe4 and SnEt4). A phototransistor detector was also used to detect organic substances reaching the flame atomiser. Elimination of the interference effects amongst the analystes and those due to the organic compounds themselves was successful. Large volumes of solvent may affect the signal of a given analyte by quenching if they have the same retention time. This can be overcome by the choice of a suitable solvent. Detection limits (3σ) of 10 pg of Se, 30 pg of Pb and 50 pg of Sn were obtained.

Reversible optical waveguide sensor for ammonia vapors

A small glass capillary tube was fitted with a light-emitting diode and a phototransistor detector to form a multiple-reflecting optical waveguide device. When the capillary was coated with a thin solid film composed of an oxazine perchlorate dye, the device was demonstrated to be capable of reversibly sensing ammonia vapors. Ammoniavapor concentrations from 1000 parts in 10(6) (ppm) to less than 60 ppm were easily and reproducibly detected. A preliminary qualitative kinetic model is proposed to describe the vapor-film interaction.

Burst noise in phototransistor optical isolators

Noise measurements were performed on several commercially available optical isolators in order to examine the signal detection limits of typical devices. It was found that, in general, optical isolators are very noisy devices exhibiting all of the common types of noise usually found in bipolar junction transistors. A large number of devices exhibited burst noise which dominated their low-frequency noise performance. Experimental data indicates that the source of burst noise is the phototransistor detector. A comparison of experimental data to existing burst noise theory is presented.