A novel 3C-SiC on Si power Schottky diode design and modelling
- PDF / 930,941 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 32 Downloads / 204 Views
A novel 3C-SiC on Si power Schottky diode design and modelling Fan Li1, Yogesh K. Sharma1, Craig A. Fisher1, Michael R. Jennings1 and Philip A. Mawby1 1 School of Engineering, University of Warwick, Library Road, Coventry, CV4 7AL, UK. ABSTRACT Although 3C-SiC has a narrower bandgap than 4H-SiC, it is the only SiC polytype that can be grown directly over large area silicon substrates. It has the potential to provide a more economical choice than 4H-SiC for intermediate power devices, such as inverters for electric vehicles. To fabricate a vertical device on 3C-SiC, the Si substrate is usually removed either by etching or polishing. Neither of these processes is economical nor efficient. In this paper we propose a lateral Schottky diode design for 3C-SiC on Si structure. 2D finite element simulations using ATLAS showed that a breakdown voltage beyond 1200 V can be achieved with a 4 µm thick epilayer. Physical models used for 3C-SiC/Si power devices simulations are introduced. Advantages of lateral 3C-SiC/Si diodes over free standing 3C-SiC are also discussed. INTRODUCTION Due to their superior electrical properties, SiC power devices are more efficient than their Si counterparts at higher voltages, frequencies and temperatures. In spite of their obvious advantages in high voltage applications, cost and reliability issues make SiC much less competitive in intermediate voltage (600-1200 V) FET design [1]. Compared with Si devices fabricated on 200 mm or even larger wafers, 4H-SiC wafers are currently limited to 150 mm. On the other hand, 300 mm 3C-SiC/Si wafers has already been demonstrated [2]. The latest material growth development has led to high quality 3C-SiC epitaxial layers with planar defect (stacking fault) densities lower than 400 cm-3 [3]. These are encouraging signs to enable SiC technology to be more cost-effective. 3C-SiC has a narrower bandgap than 4H-SiC, but it is still two times higher than Si, and has more isotropic electrical properties than 4H-SiC as a result of its cubic structure. The thermal conductivity of 3C-SiC is comparable with that of 4H-SiC, although the intrinsic carrier concentration is higher, which means 3C-SiC is less suitable for high temperature operation. The bulk mobilities of both polytypes are similar. These properties suggest 3C-SiC is a promising material for power device design. To date, 600 V 3C-SiC vertical power devices have been reported [4, 5], but higher voltages are prohibited by the unavailability of thick high quality 3C-SiC epilayers. In this work, a novel lateral 3C-SiC/Si Schottky diode design targeting a blocking voltage of 1200 V is studied. Table I. Key properties of Si, 4H- and 3C-SiC [6, 7] Properties (at 300 K)
Si
4H-SiC
3C-SiC
Band Gap (eV)
1.12
3.26
2.4
5x10-9
1.5x10-1
Intrinsic Carrier Concentration (cm-3) 1x1010 Electron Mobility (cm2 V-1 s-1) Thermal Conductivity (W cm-1 K-1)
≈1350 ≈900 (a-axis) 1.5
4.5
≈1000 5
DESIGN THEORY Physical models One of the first requirements of designing power devices is to estimate the avalanche breakdown vo
Data Loading...
