Molecular Beam Epitaxy

23Applications of Bismuth‐Containing III–V Semiconductors in Devices

Masahiro Yoshimoto

Kyoto Institute of Technology, Sakyo, Kyoto, 606‐8585, Japan

23.1 Introduction

GaAs_1−xBi_x is considered one of the highly mismatched alloys [1], which contain elements with significantly different sizes, electronegativities, and/or ionization energies such as GaAs_1−xN_x [1], GaN_xP_1−x [2], and ZnO_1−xSe_x [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 GaN_xAs_1−x arises due to resonance between the N atom level and the conduction band of GaAs [1]. In the case of GaAs_1−xBi_x, 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 GaAs_1−xBi_x 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 (Δ_so) between the valence band and the split‐off band (inset of Figure 23.1) [11]. Further, quaternary alloys of GaN_yAs_1−x−yBi_x and In_yGa_1−yAs_1−xBi_x are narrow bandgap semiconductors which are lattice‐matched to GaAs and InP, respectively.

Figure 23.1 ...