ε‐Ga₂O₃ Thin Film Avalanche Low‐Energy X‐Ray Detectors for Highly Sensitive Detection and Fast‐Response Applications

Abstract

Low‐energy X‐ray detectors are widely used in diverse areas, including medical diagnosis, space exploration, environmental monitoring, industrial inspection, and scientific research. Developing large area, highly sensitive, and fast low‐energy X‐ray detectors is challenging owing to material and device operation mechanism limitation. Herein, an epitaxial ε‐Ga2O3 thin film over a large area (2 in.) is prepared by metal–organic chemical vapor deposition and applied in the efficient low‐energy X‐ray detectors. The detectors are highly sensitive to detecting low‐energy X‐rays owing to the high mass attenuation coefficients achieved in the low‐energy X‐ray range (1–30 keV). The avalanche multiplication mechanism in back‐to‐back Au–Ga2O3 Schottky diodes is explored to realize high carrier multiplication and photocurrent gain. The charge collection efficiency is improved by reducing the spacing gap of the fingers within the coplanar interdigitated Au electrodes in the film, thus achieving a high detection sensitivity of up to 1.9 × 104 μCGyair−1 cm−2 for 30 keV X‐ray. Furthermore, the ε‐Ga2O3 thin films demonstrate high crystallization quality with low trap density and high breakdown voltage with a low noise current that enable their usage in applications requiring fast response time (e.g., 37 ms) and low detectable dose rate (e.g., 42.3 μGyair s−1).

High-Speed and High-Responsivity Silicon/Black-Phosphorus Hybrid Plasmonic Waveguide Avalanche Photodetector

“…where V bias is the applied bias voltage, V b is the electric breakdown voltage, and n is the index corresponding to the ionization rate. 40,41 Although the theoretical model is extracted from the silicon avalanche photodiodes, 42 similar trends are observed for the present BP APD, as shown by the fitting curve with n = 8.3 in Figure 4d. The photocurrents of the PDs were characterized for both wavelengths of 1.55/1.95 μm by using the calibrated optical transmission system (see Experimental Methods and Supplementary Note 4).…”

Comprehensive Raman study of orthorhombic κ/ε-Ga2O3 and the impact of rotational domains

“…The κ phase was found to thermally transition to β only under annealing at high temperatures T > 700 − 800 • C, 14,35 allowing for applications in devices requiring sufficiently high working temperatures. To date, the orthorhombic phase has been grown successfully 36 on a number of different substrates, including Al 2 O 3 (0001), GaN (0001), AlN (0001), 6H-SiC or β -Ga 2 O 3 (201), using halide vapour phase epitaxy, 14,37,38 atomic layer deposition, 39 metal-organic chemical vapor deposition, 15,18,22,27,30,35,37,[39][40][41][42][43][44] metal-organic vapor phase epitaxy, 1,[45][46][47][48] mist CVD 16,17,32,33,49,50 , plasma-assisted molecular beam epitaxy 51,52 , laser molecular beam epitaxy, 21,53 and pulsed laser deposition 12,13,24,[54][55][56][57] .…”

Highly Sensitive Direct‐Conversion Vacuum Flat‐Panel X‐Ray Detectors Formed by Ga2O3‐ZnO Heterojunction Cold Cathode and ZnS Target and their Photoelectron Multiplication Mechanism

“…This X-ray detection sensitivity is two orders of magnitude higher than that of the literature-reported amorphous Ga 2 O 3 thin film (6.77 μCGy air −1 cm −2 ) or polycrystalline Ga 2 O 3 thin film (2.78 μCGy air −1 cm −2 ) based X-ray detectors. [23,29] In addition, the proposed X-ray detector offers advantages including a large area (5 cm 2 ), a low dark current (50 pA mm -2 at 9.2 V μm -1 electric field) and a fast response speed (rise time: 5.3 ms), significantly outperforming the reported X-ray detectors based on singlecrystal Ga 2 O 3 thin film [28] or single-crystal bulk Ga 2 O 3 substrate. [36] The a-Se photoconductor is an ideal material for use in low-energy X-ray detectors with large area, low dark current and fast response, but the achieved X-ray detection sensitivity (22.5 μCGy air −1 cm −2 ) is limited due to its relatively low X-ray absorption efficiency and high EHP production energy.…”

“…Ga 2 O 3 photoconductors are ideal materials for low-energy X-ray detection and imaging due to the high mass attenuation coefficients throughout the low-energy X-ray range (1-30 keV). [28] Therefore, the J-E characteristics of detector #2 were measured under different X-ray energies to further optimize the X-ray detection sensitivity (Figure 5a). The dark current density of detector was 49.9 pA mm -2 at 9.2 V μm -2 , and the corresponding photocurrent density increased from 59.9 to 151.9 pA mm -2 when the X-ray energy increased from 6 to 50 keV.…”