Abstract
Hall-effect in semiconductors has wide applications for magnetic field sensing. Yet, a standard Hall sensor retains two problems: its linearity is affected by the non-uniformity of the current distribution; the sensitivity is bias-dependent, with linearity decreasing with increasing bias current. In order to improve the performance, we here propose a novel structure which realizes bias-free, photo-induced Hall sensors. The system consists of a semi-transparent metal Pt and a semiconductor Si or GaAs to form a Schottky contact. We systematically compared the photo-induced Schottky behaviors and Hall effects without net current flowing, depending on various magnetic fields, light intensities and wavelengths of Pt/GaAs and Pt/Si junctions. The electrical characteristics of the Schottky photo-diodes were fitted to obtain the barrier height as a function of light intensity. We show that the open-circuit Hall voltage of Pt/GaAs junction is orders of magnitude lower than that of Pt/Si, and the barrier height of GaAs is smaller. It should be attributed to the surface states in GaAs which block the carrier drifting. This work not only realizes the physical investigations of photo-induced Hall effects in Pt/GaAs and Pt/Si Schottky junctions, but also opens a new pathway for bias-free magnetic sensing with high linearity and sensitivity comparing to commercial Hall-sensors.
Highlights
The Hall effect in semiconductors has been used for more than one century to detect the intensity of magnetic fields [1]
Magneto-resistive sensors in digital systems have been developed in recent years, semiconductor Hall sensors still retain irreplaceable in analog applications because of their two specific features: (1) they are intrinsically linear, and do not need magnetic materials; (2) their sensitivity is directly proportional to the bias current [2,3,4,5,6,7]
Commercial Hall sensors have to operate by using a very low bias current, because linearity decreases with increasing bias-current [8]
Summary
The Hall effect in semiconductors has been used for more than one century to detect the intensity of magnetic fields [1]. The carriers in semiconductor are injected into metal at a very high velocity, much faster than diffusion [13] In this case, if a magnetic field is applied in the plane of a Schottky diode, it can generate large Lorentz forces and produce a transverse, open-circuit voltage at the metal edges that is proportional to the field, as well as light intensity. For a traditional lateral photo-diode, light is photo-converted into the increasing of an existed electrical current in a standard device [14,15,16,17] It consist of an extended p-type/intrinsic/ntype (p-i-n) semiconductor tri-layer with a bottom cathode electrode and four top lateral anodes. In our device, light only reduces the built-in potential of the Schottky-barrier, with no net current flowing This allows our sensor to operate in open-circuit conditions to recover linearity without increasing cost. There is no net current in the circuit, so its performances are not affected by bias current
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