Band anticrossing in dilute nitrides

Alloying III–V compounds with small amounts of nitrogen leads to a dramatic reduction of the fundamental band-gap energy in the resulting dilute nitride alloys. The effect originates from an anticrossing interaction between the extended conduction-band states and localized N states. The interaction splits the conduction band into two non-parabolic subbands. The downward shift of the lower conduction subband edge is responsible for the N-induced reduction of the fundamental band-gap energy. The changes in the conduction band structure result in a significant increase in electron effective mass and a decrease in the electron mobility, and lead to a large enhancement of the maximum doping level in GaInNAs doped with group VI donors. In addition, a striking asymmetry in the electrical activation of group IV and group VI donors can be attributed to mutual passivation process through formation of the nearest neighbour group-IV donor nitrogen pairs.