Impact of short‐range order and clusterization on the bandgap bowing: First‐principles calculations on the electronic properties of metastable (GaAs)_1–x(Ge₂)_x alloys

Abstract

The large, negative, and asymmetric bandgap bowing in (GaAs) 1-x (Ge 2 ) x alloys is investigated as function of Ge concentration, via the combination of density functional theory and GW 0 approach. We revealed that the large negative character of the gap bowing is due to the increase of the octetrule violating bonds (bad bonds) as Ge reaches intermediate concentrations, while the asymmetry is governed by the presence of GaAs clusters embedded in the Ge matrix at Ge concentration between 0.3 and 1. Both the clusterization and fragmentation of GaAs region are phenomena able to delocalize the extracharges on the formed bad bonds, causing thermodynamic stabilization, and bandgap increase. Our results are in very good agreement with the experimental ones, confirming the bandgap bowing dependency on the nearest-neighbor atomic interactions.

Study of percolation and modeling of the order–disorder transition for zincblende–diamond structures: Percolation and the existence of a unique band of events

“…In the case of zincblendeediamond transition the value obtained using our simulations for the (111) direction x c ¼ 0.451 ± 0.030 is not in agree with the previous reported values [4,5,17]. The morphology of system is influenced by the concentration of IV atoms, this results agree with theoretical calculations reported by Kawai et al [6] and Giorgi et al [1].…”

“…Recently, Kawai et al [6], and Giorgi et al [1] studied the large, negative, and asymmetric band gap bowing in (GaAs) 1Àx (Ge 2 ) x alloys is investigated as function of Ge concentration, by using the combination of density functional theory and GWo approach. They found that the large negative character of the gap bowing is due to the increase of the octetrule violating bonds (bad bonds) as Ge reaches intermediate concentrations, while the asymmetry is governed by the presence of GaAs clusters embedded in the Ge matrix at Ge concentration between 0.3 and 1.…”

Synthesis and Structural and Optical Properties of Ga(As1–xPx)Ge3 and (GaP)yGe5–2y Semiconductors Using Interface-Engineered Group IV Platforms

“…On the other hand, the disappearance of emission for x > 0.2 is intriguing. Studies of (GaAs) 1– x Ge 2 x alloys suggest that the large negative bowing of the band gap in this system correlates with a strong valence band localization on the As atoms . This may not be the case with P, and if so, III–P–Ge compounds may not share the anomalously low band gap observed in compounds such as (GaAs) 1– x Ge 2 x or (GaSb) 1– x Ge 2 x .…”

“…Studies of (GaAs) 1−x Ge 2x alloys suggest that the large negative bowing of the band gap in this system correlates with a strong valence band localization on the As atoms. 23 This may not be the case with P, and if so, III−P−Ge compounds may not share the anomalously low band gap observed in compounds such as (GaAs) 1−x Ge 2x or (GaSb) 1−x Ge 2x . 24 The nature of the lowest band gap of P-rich Ga(As 1−x P x )Ge 3 alloys is very important from the point of view of potential applications and will be the subject of future research.…”