Comprehensive Study on Ultra-Wide Band Gap La₂O₃/ε-Ga₂O₃ p–n Heterojunction Self-Powered Deep-UV Photodiodes for Flame Sensing

Abstract

Solar-blind UV photodetectors have outstanding reliability and sensitivity in flame detection without interference from other signals and response quickly. Herein, we fabricated a solar-blind UV photodetector based on a La 2 O 3 /ε-Ga 2 O 3 p−n heterojunction with a typical type-II band alignment. Benefiting from the photovoltaic effect formed by the space charge region across the junction interface, the photodetector exhibited a selfpowered photocurrent of 1.4 nA at zero bias. Besides, this photodetector demonstrated excellent photo-to-dark current ratio of 2.68 × 10 4 under 254 nm UV light illumination and at a bias of 5 V, and a high specific detectivity of 2.31 × 10 11 Jones and large responsivity of 1.67 mA/W were achieved. Importantly, the La 2 O 3 / ε-Ga 2 O 3 heterojunction photodetector can rapidly respond to flames in milliseconds without any applied biases. Based on the performances described above, this novel La 2 O 3 /ε-Ga 2 O 3 heterojunction is expected to be a candidate for future energy-efficient fire detection.

Tunable Ga2O3 solar-blind photosensing performance via thermal reorder engineering and energy-band modulation

“…Furthermore, the conductance of the five devices in the dark and under 254 nm illumination were calculated and the results are given in figure 4(c), from which it can be seen that before and after the illumination, the conductance of the three annealed samples rises considerably more than that of the unannealed sample, which suggests that the crystal structure of the annealed film is more favorable to the drift of the photogenerated carriers, thus improving the photoelectric conversion ability of the devices. Responsivity (R), specific detectivity (D * ) and external quantum efficiency (EQE) are key figure-of-merits to evaluate the performance of PDs, which are defined by equations when consider the shot noise from I dark as the major contribution of the total noise current [13]: where P is the light intensity, S represents the efficient illuminated area of the PD, e is electron charge, h is the Planck's constant, l is the wavelength of illuminated light, and c is the speed of light. As demonstrated in figure 4(d), when applied a 5 V bias voltage, the device based on the pristine film shows the largest EQE of 7.29%, followed by that annealed in oxygen plasma.…”

“…The desired bandgap of Ga 2 O 3 contributes to its absorption property in the solar-blind UV region [7,8]. Since solar-blind UV light is absorbed by the ozone layer in the atmosphere and is consequently barely existing at the Earth's surface, therefore, solar-blind UV photodetectors (PDs) based on Ga 2 O 3 can operate with little influence from sunlight, which enables them to have important applications in UV imaging, UV communications, flame sensing, etc [9][10][11][12][13]. In recent years, researchers have carried out in-depth studies on Ga 2 O 3 -based solar-blind UV PDs, and one of the main aspects is the tuning and optimization of their detection performance; towards actual employments [14][15][16].…”

Photogain-Enhanced Signal-to-Noise Performance of a Polycrystalline Sn:Ga2O3 UV Detector via Impurity-Level Transition and Multiple Carrier Transport

“…The ultrawide E g of Ga 2 O 3 makes it highly suitable for fabricating solar-blind ultraviolet photodetectors, which operate in the solar-blind ultraviolet waveband (200–280 nm, also known as UV–C) . These photodetectors vary according to their structures, including metal–semiconductor–metals (MSMs), heterojunctions, Schottky barrier diodes (SBDs), and others . Besides, they can work as a single device or together as an array. − Such a diversity of the device structure is possible because Ga 2 O 3 exists in five crystalline phases, α, β, γ, δ, and ε, all of which can be grown using various techniques, including laser molecular beam epitaxy (laser-MBE), pulsed laser deposition (PLD), magnetron sputtering, metal–organic chemical vapor deposition (MOCVD), atomic layer deposition (ALD), halide vapor-phase epitaxy (HVPE), and mist chemical vapor deposition (mist-CVD), providing a convenient way for its development in relevant devices.…”

“…2 The ultrawide E g of Ga 2 O 3 makes it highly suitable for fabricating solar-blind ultraviolet photodetectors, which operate in the solar-blind ultraviolet waveband (200−280 nm, also known as UV−C). 3 These photodetectors vary according to their structures, including metal−semiconductor−metals (MSMs), 4 heterojunctions, 5 Schottky barrier diodes (SBDs), 6 and others. 7 Besides, they can work as a single device or together as an array.…”

“…On the other hand, at a higher concentration of carriers, the mobility was also decreased, which also contributed to this phenomenon. Furthermore, R and external quantum efficiency (EQE) values are two critical criteria that determine the performance of a PD, which can be expressed as follows 39 = hcR e EQE (5) where h is Planck's constant, c is the light velocity, e is the electronic charge, and λ is the wavelength of incident light. An The differences in the performances of the two PDs can be theoretically interpreted by the energy-band diagram shown in Figure 6a,b.…”