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This study demonstrates the fabrication and study of a permalloy (Py)/topological insulator heterojunction, i.e., the Ni80Fe20/TI(Bi2Te3/Bi2Se3/Bi2Te2Se)/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 Ni80Fe20/Bi2Te2Se/p-Si, Ni80Fe20/Bi2Se3/p-Si, and Ni80Fe20/Bi2Te3/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. [ABSTRACT FROM AUTHOR]

Quasi-2D thin film of TI material TlBiSe2, as well as TlBiSe2/GaN configuration, have been fabricated employing the thermal evaporation technique. Raman peaks of vibrational modes were analyzed in a TlBiSe2/GaN heterojunction showing a substrate-induced signal for the surface phonon mode (SPM). The study of ultrafast kinetics of charge carriers and transient absorption spectroscopy (TAS) gave excited-state spectrum characteristics and exciton dynamics in TlBiSe2/GaN heterojunction. The electrical characterization showed that the heterojunction device exhibited a good diode nature with an excellent rectification ratio of 160. The photodetection capabilities were examined by optical power varying from 2.37 µW to 3.78 µW in the ultraviolet to near-infrared region (300–900 nm). It demonstrated maximum photoresponse at 500 nm in forward and reverse bias. The current conduction mechanism and enhancement in current under light impact were explained using energy band modeling. The present work is important in regarding the development of photodetectors of succeeding generations with a topological insulator material. [ABSTRACT FROM AUTHOR]

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.

A topological insulator has a unique graphene-like Dirac cone conducting surface state, which is excellent for broadband absorption and photodetector applications. Experimental investigations on the Bi 2 Te 3 /n-GaN heterojunction exhibited an aberrant photoelectric effect under the influence of unpolarized light. Transport measurements of the Bi 2 Te 3 /n-GaN heterojunction revealed a negative photoconductance, with a sudden increase in resistance. This was consistent with the applied range of wavelength and power used for incident light while it was contrary to the usual gap-state transition model, which states that a negative conductance is due to the trapping of charge carriers. The observed aberrant photoelectric effect seen in Bi 2 Te 3 /n-GaN heterojunction devices was due to the polycrystalline nature of the Bi 2 Te 3 topological insulator film, where the incident photon-induced bandgap in the Dirac cone surface state resulted in a negative photoelectric effect. This phenomenon opens the possibility for applications in highly sensitive photodetectors and non-volatile memories, along with employing the bandgap-opening concept in retinomorphic devices.