摘要 |
<p>A coated substrate is produced and its coating has regions (14) of high free electron density in conductive relationship with regions (12) of high electron mobility. The coating is produced by exposing the substrate to a vapour capable of epitaxially depositing both types of region. A temperature gradient is provided across the surface of the substrate and the two types of region are deposited on hotter, and cooler areas of the substrate respectively.</p> |