Transfer Doping in Diamond for Channel Doping and Electrical Contacts

This article reports on the use of transfer doping (TD) to create holes in a diamond substrate using defects in Al
₂
O
₃
that are located at an energy below the top of the diamond valence band. The energy bands of a metal-Al
₂
O
₃
-diamond structure are analyzed for use as a method to make electrical contact to the diamond. The structure is also analyzed for use as part of a field-effect transistor, where the metal acts as the gate. While it is found that the metal can easily dominate the charges in a thin Al
₂
O
₃
layer, preventing efficient TD of the diamond, we found that the use of a thick Al
₂
O
₃
layer, a high defect density, or a high work function metal can all serve to permit efficient TD. It is shown that a metal-Al
₂
O
₃
-diamond structure, utilizing a high defect density in a few nm thick Al
₂
O
₃
layer, can provide a good electrical contact to the diamond because electrons can tunnel through the Al
₂
O
₃
layer and because a high hole concentration is formed under the metal contact in the diamond substrate.