Band anticrossing in dilute nitrides

Abstract

Alloying III-V compounds with small amounts of nitrogen leads to dramatic reduction of the fundamental band-gap energy in the resulting dilute nitride alloys. The effect originates from an anti-crossing interaction between the extended conduction-band states and localized N states.The interaction splits the conduction band into two nonparabolic 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 significant increase in electron effective mass and decrease in the electron mobility, and lead to a large enhance 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 neighbor group-IV donor nitrogen pairs.

The potential of GaAsBiN for multi-junction solar cells

“…The band alignment for the GaAsBi(GaAsN)/GaAs structure has been found to be type I [15,16], which has been shown to improve solar cell efficiencies over other band alignments [23]. Figure 5 shows the band offsets and strain as a function of the N and Bi concentrations.…”

“…The significant band gap reduction due to the incorporation of Bi or N atoms into GaAs may be modelled using the band anti-crossing (BAC) theory which has been well established in the case of dilute nitrides [15]. If small quantities of nitrogen (bismuth) are added to GaAs it leads to a localized N (Bi) level.…”

Semiconductor materials for ultrafast optoelectronic applications

“…Nitrogen creates resonant donor levels in GaNAs causing the reduction of the dark resistivity of the layers, whereas acceptor levels introduced by Bi in GaBiAs can enhance the compensation of As Ga donors created during the growth of this alloy at low temperatures and increase both the dark resistivity and the electron trapping rate. Moreover, the lowest conduction subband in GaNAs is characterized by a very low electron mobility [42], in contrast with GaBiAs, where the conduction band states do not mix with the impurity states and the effect of the latter on the electron mobility is minimal.…”

Amorphous GaN<inf>1&#x2212;x</inf>As<inf>x</inf> alloys for multi-junction solar cells

“…In the case of substituting the anion with a more electronegative element, such as nitrogen in the arsenic site of GaAs, it has been shown the nitrogen forms a localized level resonant with the conduction band [10][11][12]. The interaction between the localized nitrogen level and the extended states of the conduction band can be treated as a simple perturbation between two degenerate energy levels.…”