Photoluminescence Investigation of Defects Created by Electron Bombardment of 4H-SiC

Use of a transmission electron microscope to irradiate silicon carbide samples has been demonstrated as a useful additional characterisation technique. The photoluminescence spectra of crystal defects introduced in this way have been found to be extremely rich in detail, involving more than 50 zero phonon lines. It is perhaps disappointing that relatively few of these optical centres have been identified conclusively. Indeed, controversy exists over most of the interpretations that have been advanced. As a step towards clarifying this situation we have been studying many of the more important photoluminescent systems by investigating the dependence of the results on the sample n- and p-doping levels, their stoichiometry, the source of supply, the electron dose, the subsequent annealing history, and by exploiting two new aspects of the technique that will be introduced here. A brief review will be given of new results obtained for some of the major optical centres. Most of the irradiations have been performed at room temperature using 300 kV electrons but some were carried out at 750°C.

Laser Direct Write of Conducting and Insulating Tracks in Silicon Carbide

ABSTRACTConventional direct write processes are multi-step requiring at least one additional process to change conductive properties. A direct conversion technique that uses lasers to irradiate silicon carbide, providing tracks which are highly conductive has been demonstrated. It was found that laser irradiation of insulating silicon carbide films could cause a drop from 1011 to 10−4 ohm-cm in a 4-point resistance test. However, in the presence of pure oxygen, laser-irradiated silicon carbide conductor and semiconductor samples exhibit insulating characteristics. Pattern formation was achieved by a computer program controlled galvo-mirror. The pads, 0.4 cm × 0.7 cm were formed by beam rastering with an overlap of 30% of the 0.025 cm beam diameter. This computer assisted processing allows the design of patterns using conventional CAD/CAE technologies and smart material behavior via selective and controlled electrical property transitions by laser irradiation