ffiEE zyxwvutsrqponm TRANSACTIONS ON zyxwvutsrqp MAGNETICS, VOL. 28, NO. 5, SEPTEhfBER zyxwvuts 1992 2193 A New Magnetic Sensor Using Separated Drift Field Seung-Ki Lee, Kwang-Hoon Oh, Uk-Song Kang, and Min-Koo Han Department of Electrical Engineering, Seoul National University Seoul 15 1-742, Korea zyxwvut Abstract-A novel magnetotransistor using a separated drift field has been designed and fabricated. The measured relative sensitivity of the magnetotransistor agrees well with the analyticalvalue based on the emitter injection modulation model. In the saturation mode, the relative sensitivity is extremely increased by the drift of electrons due to the lateral field in the emitter. I. INTRODUCTION Magnetotransistors are a promising magnetic sensor due to their high sensitivity [l]. The widely used operating principles of magnetotransistors are emitter injection modulation and carrier deflection [2,3]. A large increase in sensitivity of magnetotransistors can be achieved using emitter injection modulation. However, there were some experimental and numerical results which indicate that emitter injection modulation can be ruled out as an operating principle [4]. On the contrary, a recent study [SI shows that emitter injection modulation is related to the drift carrier transport and it is necessary to separate the electric field with the junction behavior in order to utilize the emitter injection modulation as the operating principle of the magnetotransistor. We fabricated a magnetotransistor which has a separated drift field in the emitter and analyzed its characteristics by use of the emitter injection modulation. 11. STRUCTURE AND PRINCIPLE The new magnetotransistor employs the lateral NPN bipolar transistor as shown in Fig. 1. Through the two emitter contacts, lateral electric field is applied to the emitter in the x direction. Four base contacts are located parallel to the emitter contacts in order to maintain a uniform emitter-base junction bias along the emitter edge by Manuscript received February 17, 1992. This work was supported in part by the Korean Ministry of Science and Technology. applying the identical lateral electric field in the base. The trapezoid shape of collectors is considered to prevent nonuniform emitter injection along the emitter edge since the effective base width varies due to the different reverse voltages between the upper and lower base-collector junction. When the magnetic field is applied to the device as shown in Fig. 1, electrons drifted in the x direction by the lateral field in the emitter are deflected to the right side of the emitter due to the Lorentz force. The Hall voltage induced by the lateral electric field in the emitter is built up across the right and left emitter edges in the y direction. The potential difference, which is the Hall voltage, modulates the right and left emitter-base junction bias and results in the difference of the collector currents. 111. EXPERIMENT AND DISCUSSION The new magnetotransistor has been fabricated The variation of the collector current difference as employing the standard CMOS process. B E' Fig. 1. Structure of the new magnetotransistor. 0018-9464/92$03.00 zyxwvuts 8 1992 IEEE