engleski

Some properties of SiC wide bandgap semiconductors

Silicon carbide (SiC) is a semiconductor material, which may supplant silicon (Si), and gallium arsenide (GaAs) in demanding electronic applications. The outstanding material properties of SiC allow the realization of devices, which offer tremendous benefits over other semiconductor devices in several specialized areas: high power, high frequency and high temperature electronics. The superiority of SiC is founded in the large band-gap, high breakdown electrical field, high saturation drift velocity and high thermal conductivity. Also the small lattice mismatch for III-nitride (especially GaN) epitaxial layers make SiC as substrate material for blue/UV optoelectronics devices. In the late 80’ and early 90’s research institutions started with the commercial offering of high quality SiC wafers. The mono-crystalline SiC are usually prepared by (Lely method modified by Tairov and Tsvetkov 1978.) physical vapour transports (PVT), while the epitaxial layer is prepared by chemical vapour deposition (CVD). SiC crystallized in many different polytypes (3C-, 2H-, 4H-, &H-, 15R-…) and their basic physical properties, such as a variety of band-gaps (2.4 eV ≤ Eg ≤ 3.3 eV), depend on type of poly-types. Two of them, 4H- (Eg=3.27eV) and 6H-SiC (Eg=3.02eV) are more suitable for electronic devices. Polycrystalline and amorphous SiC films are also interested for investigation. We prepare the amorphous hydrogenated silicon carbide thin films, α-Si1-xCx:H, produced by magnetron sputtering, with carbon concentration in range 0 ≤ 1 (e.g. from 100% silicon to 100% carbon). In all of depositions, the source of silicon atoms is magnetron cathode, while carbon is introduced into the films during the growth, in two ways. One is co-sputtering and other is by addition of benzene into working gas. In first mentioned, magnetron cathode consists of silicon and carbon and cathode acts as a source of both types of particles. In second one, benzene vapour is introduced near the surface of growing films and carbon is build into the film through chemical reactions at the surface, enhanced by plasma-surface interactions. Among the several SiC polytypes of practical importance 6H-SiC have the biggest impact on power devices. As the electron mobility in 4H-SiC is twice that of 6H-SiC perpendicular to the c-axis and about 10 times that of 6H-SiC parallel to the c-axis, all physically based numerical device simulators are investigated on 4H-SiC based devices. Several methods of numerical semiconductor simulations are used to order the performance of device characteristics (open-base voltage blocking capability, current handling ability, switching speed) of some 4H- and 6H-SiC devices (as npn power bipolar junction transistor (BJT) or static induction transistor (SIT) and that results are compared with the last fabrication of SiC components (MESFET, BJT, JFET, SIT, thyristor, pn junction diodes). All results show that the device made with SiC has great performance advantages over those made with Si or GaAs.

SiC; high power semiconductor; large band-gap

nije evidentirano