| 1. |
- Blank, T. V., et al.
(författare)
-
Temperature dependence of the photoelectric conversion quantum efficiency of 4H-SiC Schottky UV photodetectors
- 2005
-
Ingår i: Semiconductor Science and Technology. - : IOP Publishing. - 0268-1242 .- 1361-6641. ; 20:8, s. 710-715
-
Tidskriftsartikel (refereegranskat)abstract
- Ultraviolet Schottky photodetectors based on n-4H-SiC (N-d - N-a = 4 x 10(15) cm(-3)) epitaxial layers of high purity have been fabricated. Their spectral sensitivity range is 3.2-5.3 eV peaking at 4.9 eV (quantum efficiency is about similar to 0.3 electron/photon), which is close to the bactericidal ultraviolet radiation spectrum. The temperature dependence of the quantum efficiency of 4H-SiC Schottky structure has been investigated to determine the temperature stability and the mechanism of the photoelectric conversion process. At low temperatures (78-175 K) the quantum efficiency increases with increasing temperature for all photon energy values and then tends to saturate. We suppose that some imperfections in the space-charge region act as traps that capture both photoelectrons and photoholes. After some time the trapped electron-hole pairs recombine due to the tunnelling effect. At high temperatures (more than 300 K), the second enhancement region of the quantum efficiency is observed in the photon energy range of 3.2-4.5 eV. It is connected with a phonon contribution to indirect optical transitions between the valence band and the M-point of the conduction band. When the photon energy is close to a direct optical transition threshold this enhancement region disappears. This threshold is estimated to be 4.9 eV. At photon energies more than 5 eV a drastic fall of the quantum efficiency has been observed throughout the temperature interval. We propose that in this case the photoelectrons and photoholes are bound to form hot excitons in the space-charge region due to the Brillouin zone singularity, and do not contribute to the following photoelectroconversion process.
|
|
| 2. |
- Kalinina, E, et al.
(författare)
-
Comparative study of 4H-SiC irradiated with neutrons and heavy ions
- 2005
-
Ingår i: SILICON CARBIDE AND RELATED MATERIALS 2004. - ZURICH-UETIKON : TRANS TECH PUBLICATIONS LTD. - 0878499636 ; , s. 377-380
-
Konferensbidrag (refereegranskat)abstract
- The influence of the irradiation with neutrons, Kr+ (245 MeV) and Bi+ (710 MeV) ions on the optical and electrical properties of high-resistivity, high-purity 4H-SiC epitaxial layers grown by chemical vapor deposition was investigated using photoluminescence and deep-level transient spectroscopy. Electrical characteristics were studied using Al and Cr Schottky barriers as well as p(+)-n-n(+) diodes fabricated by Al ion implantation on this epitaxial layers. It was found that both "light" neutrons and high energy heavy ions introduced identical defect centers in 4H-SiC. So, even at extremely high density of the ionization energy of 34 keV/mn, typical for Bi+ ion bombardment, damage structure formation in SiC single crystal is governed by energy loss in elastic collisions.
|
|
