Effect of an external/internal magnetic field on the photocurrent in Py-topological insulator heterojunction Ni 80 Fe 20 /TI (Bi 2 Te 3 /Bi 2 Se 3 /Bi 2 Te 2 Se)/p-Si devices.

This study demonstrates the fabrication and study of a permalloy (Py)/topological insulator heterojunction, i.e. , the Ni 80 Fe 20 /TI(Bi 2 Te 3 /Bi 2 Se 3 /Bi 2 Te 2 Se)/p-Si heterojunction, for spintronic device applications at room temperature. In this work, the forward current values, under the absence of a magnetic field, for Ni 80 Fe 20 /Bi 2 Te 2 Se/p-Si, Ni 80 Fe 20 /Bi 2 Se 3 /p-Si, and Ni 80 Fe 20 /Bi 2 Te 3 /p-Si heterojunctions were 12.7 μA, 8.7 μA, and 6.85 μA, respectively; while in the presence of a magnetic field, the corresponding values were 10.8 μA, 7.6 μA, and 4.47 μA, respectively. Such reductions in current were attributed to an increase in the resistance of the p-n junction diode due to Lorentz force and a magnetoresistance effect, which was also verified using magneto-transport measurements. This resulted in a modification of the space charge shape and an increase in the potential barrier. Along with this, the magnetic field also affected the diffusion length, leading to a reduction in the current. Such a phenomenon enables the development of durable devices with improved reliability and longevity under harsh environments. The special features of topological edge states in the presence of a magnetic field can be used for sophisticated sensing applications. The future applications will likely lead to the emergence of other novel applications across disciplines such as computing, health, materials science, and energy harvesting.