Abstract:In this work, a single-crystalline β-Ga2O3 epilayer was grown on (0001) sapphire at low temperature by low-pressure metal organic chemical vapor deposition. The optimized parameters for the chamber pressure, oxygen flow, and growth temperature were 15 Torr, 200 sccm, and 500 °C, respectively. The β-Ga2O3 epilayer was fabricated as a metal-semiconductor-metal solar-blind deep ultraviolet photodetector. Due to the gallium oxide grown at low temperature, the as-grown β-Ga2O3 epilayer was annealed at 800 °C in atm… Show more
“…They were responsible in trapping the photogenerated electron or hole carriers. The smooth surface would lead to the low surface area and then the low surface density states for the annealed ZnGa 2 O 4 film, which is beneficial for the improved performance of the PD 14,15 .Figure 2Atomic force microscope images of thin-film surfaces and surface roughness of as-grown and annealed ZnGa 2 O 4 thin films.…”
Section: Resultsmentioning
confidence: 99%
“…High Idark for as-grown ZnGa 2 O 4 films can be inter-related to the high intrinsic defects, such as oxygen vacancies and/or surface density state in the ZnGa 2 O 4 films. The low photocurrent implied that the defect concentration was reduced, which resulted in low conductivity 15 . Surface-related defects can act as adsorption sites or trapping center to capture free electrons in ZnGa 2 O 4 films.…”
A single-crystalline ZnGa2O4 epilayer was successfully grown on c-plane (0001) sapphire substrate by metal-organic chemical vapor deposition. This epilayer was used as a ternary oxide semiconductor for application in high-performance metal–semiconductor–metal photoconductive deep-ultraviolet (DUV) photodetectors (PDs). At a bias of 5 V, the annealed ZnGa2O4 PDs showed better performance with a considerably low dark current of 1 pA, a responsivity of 86.3 A/W, cut-off wavelength of 280 nm, and a high DUV-to-visible discrimination ratio of approximately 107 upon exposure to 230 nm DUV illumination than that of as-grown ZnGa2O4 PDs. The as-grown PDs presented a dark current of 0.5 mA, a responsivity of 2782 A/W at 230 nm, and a photo-to-dark current contrast ratio of approximately one order. The rise time of annealed PDs was 0.5 s, and the relatively quick decay time was 0.7 s. The present results demonstrate that annealing process can reduce the oxygen vacancy defects and be potentially applied in ZnGa2O4 film-based DUV PD devices, which have been rarely reported in previous studies.
“…They were responsible in trapping the photogenerated electron or hole carriers. The smooth surface would lead to the low surface area and then the low surface density states for the annealed ZnGa 2 O 4 film, which is beneficial for the improved performance of the PD 14,15 .Figure 2Atomic force microscope images of thin-film surfaces and surface roughness of as-grown and annealed ZnGa 2 O 4 thin films.…”
Section: Resultsmentioning
confidence: 99%
“…High Idark for as-grown ZnGa 2 O 4 films can be inter-related to the high intrinsic defects, such as oxygen vacancies and/or surface density state in the ZnGa 2 O 4 films. The low photocurrent implied that the defect concentration was reduced, which resulted in low conductivity 15 . Surface-related defects can act as adsorption sites or trapping center to capture free electrons in ZnGa 2 O 4 films.…”
A single-crystalline ZnGa2O4 epilayer was successfully grown on c-plane (0001) sapphire substrate by metal-organic chemical vapor deposition. This epilayer was used as a ternary oxide semiconductor for application in high-performance metal–semiconductor–metal photoconductive deep-ultraviolet (DUV) photodetectors (PDs). At a bias of 5 V, the annealed ZnGa2O4 PDs showed better performance with a considerably low dark current of 1 pA, a responsivity of 86.3 A/W, cut-off wavelength of 280 nm, and a high DUV-to-visible discrimination ratio of approximately 107 upon exposure to 230 nm DUV illumination than that of as-grown ZnGa2O4 PDs. The as-grown PDs presented a dark current of 0.5 mA, a responsivity of 2782 A/W at 230 nm, and a photo-to-dark current contrast ratio of approximately one order. The rise time of annealed PDs was 0.5 s, and the relatively quick decay time was 0.7 s. The present results demonstrate that annealing process can reduce the oxygen vacancy defects and be potentially applied in ZnGa2O4 film-based DUV PD devices, which have been rarely reported in previous studies.
“…On account of the intrinsic lower dark current and faster response speed, MSM photodetectors based on β‐Ga 2 O 3 have attracted grand interest and been extensively studied recently . Heretofore, various electrode materials including Ti/Au, Ni/Au, indium zinc oxide (IZO), and graphene have been utilized to form Schottky barrier contacts with β‐Ga 2 O 3 .…”
Due to its significant applications in many relevant fields, light detection in the solar-blind deep-ultraviolet (DUV) wavelength region is a subject of great interest for both scientific and industrial communities. The rapid advances in preparing high-quality ultrawide-bandgap (UWBG) semiconductors have enabled the realization of various high-performance DUV photodetectors (DUVPDs) with different geometries, which provide an avenue for circumventing numerous disadvantages in traditional DUV detectors. This article presents a comprehensive review of the applications of inorganic UWBG semiconductors for solar-blind DUV light detection in the past several decades. Different kinds of DUVPDs, which are based on varied UWBG semiconductors including Ga 2 O 3 , Mg x Zn 1−x O, III-nitride compounds (Al x Ga 1−x N/AlN and BN), diamond, etc., and operate on different working principles, are introduced and discussed systematically. Some emerging techniques to optimize device performance are addressed as well. Finally, the existing techniques are summarized and future challenges are proposed in order to shed light on development in this critical research field.with energy much higher than the semiconductor bandgap. Moreover, due to light absorption by the surface passivation layers, typically Si oxide, quantum efficiency in the DUV range is greatly reduced. The passivation layers are also easily degraded by UV illumination. Finally, for highly sensitive UV photodetection, the detectors need to be cooled to reduce dark current; the cooled detectors, however, behave like cold traps for contaminants which degrade the detectivity.In the past two decades, the emergence of UV photodetectors based on wide-bandgap (WBG) semiconductors has opened up an avenue to circumvent the above-mentioned dilemma. The WBG semiconductors such as SiC, GaN, and some group II-V compounds, typically have bandgaps exceeding ≈3.10 eV, enabling room-temperature detectors to possess fast response speed, and offering intrinsic visible-blindness (response cutoff wavelength: ≈400 nm). [14][15][16] Moreover, these semiconductors generally possess significantly higher thermal conductivity than Si, which renders them suitable for operation in harsh environments (e.g., high temperature and high power). The electron velocity of these materials at large electric fields is generally higher than that of common semiconductors, although WBG semiconductors exhibit relatively lower electron and hole mobilities. Compared with the abovementioned conventional WBG semiconductors, ultrawide-bandgap (UWBG) semiconductors, as the next generation of semiconductor materials with bandgaps significantly wider than the 3.4 eV of GaN, are particularly suitable for solar-blind DUV light detection. [17][18][19][20]
“…Huang et al annealed the epilayer at 800°C under different ambient to improve the crystallinity and found that the X-ray diffraction of β-Ga 2 O 3 annealed in a nitrogen environment for 15 min has the strongest peak while annealing in an oxygen environment for 30 min shows diminished performance due to the oxygen content reaching a saturation state during annealing. In air ambient annealing which used both oxygen and nitrogen, the observed crystalline properties were better than those obtained from purely oxygen annealing [13]. Up to now, no reports have systematically studied the annealing effect of (GaIn) 2 O 3 films.…”
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