High-Responsivity Deep-Ultraviolet-Selective Photodetectors Using Ultrathin Gallium Oxide Films

Abstract

Wavelength-selective photodetectors responding to deep-ultraviolet (DUV) wavelengths (λ = 200−300 nm) are drawing significant interest in diverse sensing applications, ranging from micrometer biological molecules to massive military missiles. However, most DUV photodetectors developed thus far have suffered from long response times, low sensitivity, and high processing temperatures, impeding their practical use. Here, we report fast, high-responsivity, and general-substrate-compatible DUV photodetectors based on ultrathin (3−50 nm) amorphous gallium oxide (GaO X ) films grown by low-temperature (∼<250 °C) atomic layer deposition (ALD) for the first time. ALD-grown GaO X films on glass substrates display a typical amorphous nature, which is identified by electron beam diffraction and X-ray diffraction measurements, while their band gap is sharply featured at ∼4.8 eV. Metal−semiconductor−metal photodetectors (active area of 30 × 30 μm 2 ) using the 30-nm-thick GaO X films work reliably only for DUV wavelengths; the responsivity is maximized to 45.11 A/W at λ = 253 nm, which dropped off at λ ≈ 300 nm (i.e., a cutoff wavelength). The dark current measured at 10 V is as low as 200 pA and the signal-to-noise ratio reaches up to ∼10 4 , underpinning the pristine material quality of the ALD-grown GaO X films. In addition, the rise time (i.e., the time interval for photocurrent to increase from 10% to 90%) is as quick as 2.97 μs at λ = 266 nm. Such a reliable and fast photoresponse is achieved for even atomically thin (∼3 nm) devices. The substrate-compatible and low-temperature ALD growth permits the demonstration of flexible DUV photodetectors using amorphous GaO X films grown on polyimide substrates, suggesting their facile integration into other curved optoelectronic systems. We believe that photodetectors developed herein will provide an economically viable solution for high-performance DUV detection and create a variety of sensing applications.

Self-powered MSM deep-ultraviolet β-Ga2O3 photodetector realized by an asymmetrical pair of Schottky contacts

“…Metal oxides with unique optoelectronic and chemical properties, are always been exploited to various applications [6][7][8]. Recently, monoclinic Ga 2 O 3 (β-Ga 2 O 3 ) with a wide bandgap of 4.9 eV, possessing the merits of high carrier mobility, low-cost, easily synthesized, high physical and chemical stability, has been numerously applied for power and optoelectronic devices [9][10][11][12][13].…”

Demonstration of zero bias responsivity in MBE grown β-Ga2O3 lateral deep-UV photodetector

“…Excellent solar-blind performance with high responsivity and low dark currents have been reported for β-Ga 2 O 3 deep-UV photodetectors. 6,[26][27][28][29][30][31][32] Both Schottky 14,17,27,30,[32][33][34] and metal-semiconductor-metal (MSM) 7,9,13,[19][20][21]35,36) type device architecture have been studied on bulk as well as epitaxial β-Ga 2 O 3 on foreign substrates. Battery-free, self-powered UV detectors reduce the weight and power supply requirement of imagers and prove to be beneficial in terms of reducing the footprint and complexity of systems.…”

Low dimensional freestanding semiconductors for flexible optoelectronics: materials, synthesis, process, and applications

“…Although there has been an increasing amount of attention on single-crystal β-Ga 2 O 3 for flexible applications [111], it is still possible to use amorphous GaO x thin films for various devices. This device demonstrates a detection capability over UV wavelengths in the range of 200-300 nm, with a peak responsivity of 45.11 A/W a 235 nm, and can withstand bending with a radius as low as 14 mm with stable performance [112]. SnTe is an additional material from which Q2D photodetectors can be fabricated, integrating nanoflakes instead of NMs.…”