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

Takashi Manago,Kenji Kasahara,Ichiro Shibasaki

doi:10.1063/5.0039809

Abstract

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).

Highlights

Thin film Hall elements using InSb are widely distributed worldwide in many electronic and information devices for magnetic sensor applications, and more than 1 × 109 sensors are used every year
The Fermi level pining of the backside of the GaAs substrate occurs, the band bending toward backside is very slight because the distance between the quantum wells (QWs) and the backside is so far
The bottom of the conduction band of the active layer falls in energy lower than EF and enough electrons can be supplied in the well even at 4.2 K

Summary

INTRODUCTION

Scitation.org/journal/adv threading dislocations in an active layer (InSb layer), which contributes to the improvement of the electron mobility of the active layer. To exactly match the lattice constants between the buffer and active layers, Sb atoms of the active layer were partially substituted by As atoms so that the active layer was changed into InAs0.1Sb0.9.10–12 We confirmed that the lattice mismatch between Al0.1In0.9Sb and InAs0.1Sb0.9 is almost 0 by x-ray diffraction Another good thing of substitution by As atoms in the active layer is that it realizes a smaller bandgap than InSb because of the band bowing effect, which exhibits nonlinearity with respect to the alloy composition between InSb and InAs, and higher mobility is expected. We calculate the band diagrams of various combinations of active (InAsxSb1−x) and barrier (AlyIn1−ySb) layers covering a large range of compositions These results suggest the recommended compositions of the InAsxSb1−x/AlyIn1−ySb QWs for Hall elements. The calculation results based on these assumptions well explained our experimental results.

RESULTS AND DISCUSSIONS

CALCULATION PROCEDURES

CONCLUSION