Band gap reduction in InAsN alloys

We report the structural, electrical and optical properties of bulk InAsN alloy with various nitrogen contents deposited on (100) InP substrates using plasma-assisted gas-source molecular beam epitaxy. From absorption measurements, it is found that the fundamental absorption energy of InAsN is higher than that of InAs due to the Burstein-Moss effect resulting from the high residual carrier concentration in InAsN. To deduce the 'real' band-gap energy of InAsN samples, the energy shift due to the Burstein-Moss effect and the band-gap narrowing effect are calculated by using a self-consistent approach based on the band-anticrossing (BAC) model [Shan et al.: Phys. Rev. Lett. 82 (1999) 1221]. After correction, the 'real' band-gap energy of InAsN samples decreases as N increases. The electron effective mass of InAsN is also investigated by plasma-edge measurement. We found a sizeable increase of the electron effective mass in these InAsN alloys, which is consistent with the theoretical predictions based on the BAC model.