High-performance 4H-SiC based metal-semiconductor-metal ultraviolet photodetectors with Al2O3∕SiO2 films

Abstract

4H-silicon carbide ͑SiC͒ metal-semiconductor-metal ͑MSM͒ ultraviolet ͑UV͒ photodetectors with Al 2 O 3 / SiO 2 ͑A/S͒ films employed as antireflection/passivation layers have been demonstrated. The devices showed a peak responsivity of 0.12 A / W at 290 nm and maximum external quantum efficiency of 50% at 280 nm under 20 V electrical bias, which were much larger than conventional MSM detectors. The redshift of peak responsivity and response restriction effect were found and analyzed. The A/S/4H-SiC MSM photodetectors were also shown to possess outstanding features including high UV to visible rejection ratio, large photocurrent, etc. These results demonstrate A/S/4H-SiC photodetectors as a promising candidate for OEIC applications. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2949318͔Silicon carbide ͑SiC͒ is a promising material for both optoelectronic and power devices due to its properties such as wide band gap, high break down electric field, and high thermal stability. SiC based photodetectors [1][2][3][4][5][6] have been fabricated for ultraviolet ͑UV͒ detection applications in chemical sensing, ozone-hole sensing, flame detection, etc. Planar metal-semiconductor-metal ͑MSM͒ photodetectors were considered to be more suitable for optoelectronic integrated circuits ͑OEIC͒ than p-i-n and avalanche detectors.7 Therefore, it is important to fabricate high-performance 4H-SiC based MSM photodetectors for OEIC application.However, 4H-SiC MSM photodetectors suffered from low responsivity and quantum efficiency 6 ͑QE͒ due to the optical losses including reflection and effects of surface states. Therefore, Al 2 O 3 / SiO 2 ͑A/S͒ films were selected as antireflection coatings and passivation layers on the detectors in order to reduce these losses.8 Al 2 O 3 and SiO 2 are the most important oxide film materials with the least absorption in the UV spectral region.9 Furthermore, the refractive index of Al 2 O 3 ͑n 1 ͒ films is most suitable for 4H-SiC substrates 10 in the UV region. The SiO 2 film was prepared to enhance the wavelength selectivity and adhesion between the Al 2 O 3 film and 4H-SiC substrate as well as to passivate the interface. Thus the A/S films were considered to be the most promising antireflection/passivation coatings to improve the performance of 4H-SiC MSM photodetectors. In this letter, we demonstrated A/S/4H-SiC MSM photodetectors with much better responsivity, higher QE, and larger photocurrent than conventional 4H-SiC MSM devices. The MSM photodetectors with A/S films and thermally grown layers were fabricated, respectively, for comparison on two identical n-type 4H-SiC wafers with a 3.4 m n − epilayer ͑N D = 3.1ϫ 10 15 cm −3 ͒ grown on a n + substrate ͑N D =10 20 cm −3 ͒. The orientations of the substrate and epilayer were both 8°off the ͑0001͒ Si face. The wafer for SiO 2 / 4H -SiC ͑S/4H-SiC͒ was oxidized at 1150°C for 1 h, and then etched by hydrofluoric acid in order to form a fresh surface before oxidation. Immediately, the wafer was oxidized at 1150°C for 4 h. The S/4H-SiC structur...

High-performance 4H-SiC-based p-i-n ultraviolet photodiode and investigation of its capacitance characteristics

“…Recently, a great deal of research has been carried out to develop highperformance 4H-SiC UV photodiodes with varieties of device structures, such as Schottky [3,4], metal-semiconductor-metal [5,6], p-n junction [7], p-i-n junction [8], and avalanche photodiodes [9]. Among these structures, p-i-n photodiodes are of particular interest due to a lot of advantages: low and constant capacitance, low dark current, high speed response, and high photosensitivity.…”

Pulse laser deposition of epitaxial TiO 2 thin films for high-performance ultraviolet photodetectors

“…As compared to other epitaxial wide bandgap semiconductors, such as SiC, GaN and ZnO, etc. [17][18][19][20][21], the dark currents of the polycrystalline TiO 2 -based photodetectors in previous reports are still high due to the presence of defects such as oxygen vacancies in the polycrystalline TiO 2 films. The problem of oxygen vacancies is known to be characteristics of TiO 2 systems and to substantially affect the performances of TiO 2 based-device [22][23][24][25].…”

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

“…A variety of high-performance 4H-SiC photodetectors, including Schottky [1], [2], MSM [3], p-i-n [4], and avalanche [5], have been fabricated and demonstrated in applications of chemical sensing, ozone-hole sensing, flame detection, etc. 4H-SiC is also an outstanding candidate as a substrate in microelectronic and power devices, so it is important to integrate 4H-SiC-based photodetectors and microelectronic devices for optoelectronic integrated circuits (OEICs).…”

“…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]. The SiO 2 /4H-SiC (S/4H-SiC) and 0741-3106/$26.00 © 2011 IEEE A/S/4H-SiC MIS photodetectors were finished with SiO 2 and A/S films, as shown in the inset in Fig.…”