Implanted Bipolar Technology in 4H-SiC
- PDF / 66,843 Bytes
- 6 Pages / 595 x 842 pts (A4) Page_size
- 72 Downloads / 194 Views
Implanted Bipolar Technology in 4H-SiC N. G. Wright1, C. M. Johnson1, A. G. O’Neill1, A. Horsfall1, S. Ortolland1, K. Adachi1,A. P. Knights2 and P.G.Coleman3 1
Department of Electrical and Electronic Engineering, University of Newcastle, Newcastle upon Tyne, UK, NE1 7RU U.K. Tel. +44 191 222 7345, Fax. +44 191 222 8180 2 School of Electronic Engineering, Information Technology and Mathematics, University of Surrey, Guildford GU2 5XH, United Kingdom. 3 Department of Physics, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom. ABSTRACT A simple ion-implanted bipolar transistor technology in 4H-SiC is presented. Suitable for both high-voltage vertical devices and lateral high-temperature transistors (for circuit applications), the technology is based on an implanted boron p-well with nitrogen and boron (or aluminium) implanted n+ and p+ regions respectively. The effects of base doping and carrier lifetime on device performance have been studied using TCAD techniques. It is shown that understanding the strong variation of carrier concentration with temperature (due to deep activation levels) and applied field (so-called field ionization) is critical in device design optimisation. The effects of post-implant anneal conditions on the physical and electrical characteristics of the junctions are investigated. It is shown that annealing can remove much of the damage induced by high dose nitrogen implantation but that residual damage is still present. The electrical characteristics of simple BJT transistors with breakdown voltages in excess of 1000V and common-emitter gains of ~2 is related to the level of such residual damage. INTRODUCTION SiC is an attractive candidate for manufacturing power switching devices operating at high temperature, high voltage and high current density because of its wide band-gap, high thermal conductivity and high breakdown electric field strength. Although much progress has been made in many areas of device technology, the development of a controlled, normally-off, switching device has been hampered by poor MOSFET performance. This is particularly the case with the 4H polytype, which is preferred for vertical switching devices on account of its higher on-axis mobility. Alternative majority carrier switching device technologies, such as the ACCUFET [1] and SIT, have been proposed but they demand non-trivial processing with very high tolerances to achieve acceptable performance. Bipolar switching devices, such as thyristors, and combinations of devices such as a GTO thyristor-JFET, on the other hand have been demonstrated effectively at high current levels [2]. The humble power bipolar junction transistor (BJT) has, however, received little attention, in spite of the fact it was the backbone of Si technology for many years. Simple bipolar devices have been demonstrated in SiC using multilayer epitaxial wafers [3]. Such devices show reasonable gain (typically ~10) illustrating the potential of bipolar technology in SiC. However the use of multilayer epitaxial wafers raises the cost
Data Loading...
