Composition optimization of InAsxSb1−x/AlyIn1−ySb quantum wells for Hall sensors with high sensitivity and high thermal stability

The band diagrams of InAsxSb1−x/AlyIn1−ySb quantum wells (QWs) were calculated covering a wide range of compositions of x and y. Various combinations of active (InAsxSb1−x) and barrier (AlyIn1−ySb) layers were investigated to optimize the Hall elements with high sensitivity and high thermal stability. For high sensitivity, x of 0.1–0.6 is desirable due to the band bowing effect to realize lower bandgaps compared with that of InSb in the active layer. Under the lattice matched conditions (y ∼ 1.22x), the QWs are type II QWs and the bottom of the conduction band is always lower than the Fermi level. Therefore, the QWs with x of 0.6 show large sheet carriers of 4.1 × 1011 cm−2 for 4.2 K without intentional doping, which contributes to the reduction in the temperature dependence of the transport properties. The barrier height monotonously increases with increasing y, and accordingly, the penetration depth of the wave function probability inside the barrier decreases. Under the lattice matched condition, the penetration depth drops significantly toward x = 0.4 (corresponding y ∼ 0.5) and then decreases slowly. Thus, x ≥ 0.4 (y ≥ 0.5) is preferable for a strong confinement effect, which could reduce interface scattering and, as a result, improve the electron mobility. Judging from these results, the optimized composition of the InAsxSb1−x/AlyIn1−ySb QW is x = 0.4–0.6 (under the lattice matched condition, corresponding y = 0.5–0.7).