Al2O3/SiO2 films prepared by electron-beam evaporation as UV antireflection coatings on 4H-SiC

Annealing effects on the optical and structural properties of Al2O3/SiO2 films as UV antireflection coatings on 4H-SiC substrates

“…The Si 2p peak at 101.0 and 103.8 eV were separately assigned to the 4H-SiC substrate and the SiO 2 layer. Si-suboxides peaks [17][18][19][20] were not found at the as-deposited state, which agreed with our former study [9]. Si + (Si 2p 101.8 eV) peaks were found at 550 8C and converted into Si 2+ (Si 2p 102.2 eV) peaks when the samples were annealed at 950 and 1100 8C, respectively.…”

“…The optical thicknesses of the Al 2 O 3 and SiO 2 layers were quarter-wave and half-wave for the wavelength of 275 nm, respectively. Details of deposition process have been reported elsewhere [9]. Postannealing of the three samples were performed with a fused-silica tube furnace at 550, 950 and 1100 8C, respectively for 10 min under pure N 2 atmosphere.…”

“…The refractive index of Al 2 O 3 film is most suitable for that of 4H-SiC substrate at 275 nm [8]. SiO 2 was chosen to enhance the wavelength selectivity and adhesion between the Al 2 O 3 film and 4H-SiC substrate [9]. Meanwhile, the number of film layers (usually one or two) is determined by the film absorption and manufacturing process of the semiconductor devices.…”

High-Performance 4H–SiC-Based Metal–Insulator–Semiconductor Ultraviolet Photodetectors With $\hbox{SiO}_{2}$ and $\hbox{Al}_{2}\hbox{O}_{3}\hbox{/}\hbox{SiO}_{2}$ Films

“…High-quality insulators need to be grown or deposited to reduce dark current and improve UV-to-visible rejection ratio. Electron-beam-evaporated SiO 2 and Al 2 O 3 films have low absorption in the UV spectral region and suitable refractive indices for 4H-SiC substrates [8], and the thermally grown SiO 2 formed by oxidizing a 4H-SiC substrate was proved to have good passivation property [4]. Therefore, in this letter, 4H-SiC-based MIS photodetectors, with the thermally grown SiO 2 layer and evaporated Al 2 O 3 and SiO 2 films, are designed and demonstrated to have low dark current and high UV-to-visible rejection ratio for applications.…”

“…Then, Ti(120 nm)/Al(60 nm)/Au(85 nm) and Ni(300 nm)/Au(300 nm) were separately deposited and lifted off on the SiO 2 films and backside of the 4H-SiC substrate and annealed at 950 • C in Ar for 10 min. In order to enhance antireflection effect, Al 2 O 3 (42 nm)/SiO 2 (48 nm) films were deposited by electronbeam evaporation [8] on above one wafer. The final thicknesses of Al 2 O 3 /SiO 2 (A/S) stack films on the wafer were separately quarter-wave (42 nm) and half-wave (88 nm) wavelengths of 280 nm, where the photodetectors were supposed to have peak responsivity [3].…”