If I understand, the diamond is lab grown and chemically deposited on the substrate.
Diamond material is being used to make semiconductors. The cost for that material is extremely high. Synthetically produced diamond material for semiconductor research has a price tag about 10,000 times that of silicon. Another issue is the small size of diamond wafers, with the largest commercially available size smaller than 10 square millimeters. Doping the material using ion implantation is difficult, and the material’s charge-carrier activation becomes less efficient at room temperature.