First-principles study of Nitrogen-induced band-gap reduction in III-V semiconductors

Nitrogen doping often induces the band-gap reduction for III-V semiconductors. To understand its origin, the chemical trend of reduction is studied by the first-principles calculation with comparing the cases of various III-V compounds. We found that III-V semiconductors are categorized into two groups; the large band-gap reduction occurs for InP and GaAs, while there is little reduction and appears a deep level of nitrogen in the band gap for AlAs, AlP, and GaP. It is shown that such difference reflects the order of energy positions of III-atom s-orbital state and nitrogen 3s-orbital state.