Elemental and compound semiconductors, including wide-bandgap semiconductors, are critically examined for high-power electronic applications in terms of several parameters. On the basis of an analysis applicable to a wide range of semiconducting materials and by using the available measured physical parameters, it is shown that wide-bandgap semiconductors such as SiC and diamond could offer significant advantages compared to either silicon or group III-V compound semiconductors for these applications. The analysis uses peak electric field strength at avalanche breakdown as a critical material parameter for evaluating the quality of a semiconducting material for high-power electronics. Theoretical calculations show improvement by orders of magnitude in the on-resistance, twentyfold improvement in the maximum frequency of operation, and potential for successful operation at temperatures beyond 600 degrees C for diamond high-power devices. New figures of merit for power-handling capability that emphasize electrical and thermal conductivities of the material are derived and are applied to various semiconducting materials. It is shown that an improvement in power-handling capabilities of semiconductor devices by three orders of magnitude is feasible by replacing silicon with silicon carbide; improvement in power-handling capability by six orders of magnitude is projected for diamond-based devices. >

Optimum semiconductors for high-power electronics

The formation of diamond

High-pressure synthesis of high-purity diamond crystal

Growth-sector dependence of optical features in large synthetic diamonds

The effects of applied pressure on graphite and its intercalation compounds are reviewed emphasizing the relationship between structure and transport properties. It has long been recognized that high pressure plays a crucial role in the polymorphic phase transitions of graphite, notably in the graphite-diamond transformation. More recent studies have revealed a wealth of pressure-induced phases associated with the unusual layer-stacking (‘staging’) mechanism in the intercalation compounds of graphite. The high degree of structural anisotropy associated with staging is strongly reflected in the electronic band structure and transport properties, and in the remarkable pressure dependence of the superconducting states of some of the graphite intercalation compounds. High pressure is shown to be a valuable means not only to realize new structural phases but also to improve our understanding of the fundamental behaviour of these important materials.

R. H. Wentorf

Papers

Diamond growth rates