23Applications of Bismuth‐Containing III–V Semiconductors in Devices
Masahiro Yoshimoto
Kyoto Institute of Technology, Sakyo, Kyoto, 606‐8585, Japan
23.1 Introduction
GaAs1−xBix is considered one of the highly mismatched alloys [1], which contain elements with significantly different sizes, electronegativities, and/or ionization energies such as GaAs1−xNx [1], GaNxP1−x [2], and ZnO1−xSex [3]. One of the most notable characteristics of highly mismatched alloys is a large bandgap bowing, as shown in Figure 23.1 [4–8]. The observed sharp decrease in the bandgap is due to an increase in the Bi composition and the N composition, and can be described quantitatively by the band anti‐crossing (BAC) model [ 1,9]. In the BAC model, the narrow bandgap of GaNxAs1−x arises due to resonance between the N atom level and the conduction band of GaAs [1]. In the case of GaAs1−xBix, the narrow bandgap is due to the level of Bi atom resonating with the valence band of GaAs (inset of Figure 23.1) [9]. Highly mismatched alloys of GaAs1−xBix and related semiconductors allow high flexibility in bandgap engineering and the modification of the band structure, resulting in materials with a temperature‐insensitive bandgap [10] or a large energy difference (Δso) between the valence band and the split‐off band (inset of Figure 23.1) [11]. Further, quaternary alloys of GaNyAs1−x−yBix and InyGa1−yAs1−xBix are narrow bandgap semiconductors which are lattice‐matched to GaAs and InP, respectively.