Impact of carbon and nitrogen impurities in high-κ dielectrics on metal-oxide-semiconductor devices

We investigate the electronic structure of carbon and nitrogen impurities, which are commonly incorporated during atomic-layer deposition of high-κ oxides such as Al2O3 and HfO2. The impact on metal-oxide-semiconductor devices is assessed by examining formation energies, transition levels, and band alignment between the oxide and semiconductors such as GaN, Si, and III-As. Carbon introduces charge-state transition levels near the semiconductor conduction-band edges, resulting in border traps and/or leakage current. Nitrogen acts as a source of negative fixed charge but may also be effective in alleviating the problem of carrier traps associated with native defects.