Ohmic Contacts to CVD Diamond with Boron-Doped Delta Layers

Abstract

Various methods for the formation of ohmic contacts to boron-doped δ layers in CVD-diamond epitaxial structures are investigated. In the first variant, an additional thin heavily doped layer was formed on the diamond surface to which an ohmic contact is formed. Then, the surface p⁺ layer between the contact pads is etched out; therefore, the current in the structure flows only through a buried δ layer. In the second approach, the doped diamond selectively grows in the contact windows under a metallic mask after preliminary etching of the undoped diamond layer (cap) up to the δ layer. In this case, the heavily doped p⁺ layer forms an end contact to the δ layer. These two variants differ in terms of the conditions of applicability, the complexity of the manufacturing technology, the value of the contact resistance, and can be used to solve problems in which it is necessary to have a different quality of the contacts, such as the formation of transistor structures or test cells for measuring physical characteristics.