Hyurk-Choon Kwon

MOSFET–BJT hybrid mode of the gated lateral bipolar junction transistor for C-reactive protein detection

In this study, we propose a novel biosensor based on a gated lateral bipolar junction transistor (BJT) for biomaterial detection. The gated lateral BJT can function as both a BJT and a metal-oxide-semiconductor field-effect transistor (MOSFET) with both the emitter and source, and the collector and drain, coupled. C-reactive protein (CRP), which is an important disease marker in clinical examinations, can be detected using the proposed device. In the MOSFET-BJT hybrid mode, the sensitivity, selectivity, and reproducibility of the gated lateral BJT for biosensors were evaluated in this study. According to the results, in the MOSFET-BJT hybrid mode, the gated lateral BJT shows good selectivity and reproducibility. Changes in the emitter (source) current of the device for CRP antigen detection were approximately 0.65, 0.72, and 0.80 μA/decade at base currents of -50, -30, and -10 μA, respectively. The proposed device has significant application in the detection of certain biomaterials that require a dilution process using a common biosensor, such as a MOSFET-based biosensor.

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A chemical ion sensing using a gated lateral bipolar junction transistor (LBJT) has been performed. This letter reports the basic characteristics of the proposed device and the physical differences between a pure MOSFET-based device and gated LBJT, in giving consideration to an ion sensing. The operation in the linear region, the positive polarity between input bias and output signal, and the direct proportional relationship between pH value and output signal were achieved by the bias configuration and the proposed device using an unmodified standard CMOS process. When the base current is set at -50 muA and VRG of -4 V, this device shows a sensitivity of 6.18 muA/pH.

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A method for controlling the threshold voltage which has a significant problem in ion-sensitive transistors (IST) with floating gate structures was proposed in this study. Gated lateral pnp-type bipolar junction transistor (BJT) was used in our experiment and was immerged in ionic solution. The experiment results indicated that under a large negative gate bias condition, the threshold voltage can shift in normal state with specific bias. Moreover, we discussed the reasons for the changing phenomenon of threshold voltage in dielectric of gated lateral BJT in electrolyte.

Ion-Sensitive Transistor Driving With MOS Hybrid Mode Operation

In this study, for arranging the nanorod which fabricated by electro-chemical deposition (ECD) method, a nanorod arrangement simulation had been prepared on the basis of dielectrophoresis (DEP) principle. Following the simulation a nanorod arrangement device was designed and fabricated to verify the result of the simulation. After that, nanorod was arranged on the electrodes as AC voltage loading. As the result, the rate of the nanorod arrangement was 20.35 %.

Threshold voltage changed by floating gate control in electrolyte-insulator-semiconductor structure

We present an optical current sensor for using in a harsh environment. A metal coating is plated onto the optical fiber as a heater to measure the AC electrical current. The metals used are Au and Ni-Cr. The detection method for the electric current is based on a metal film heater with a fiber-optic Fabry-Perot interferometer (FFPI). When the sensor is subjected to time-varying temperatures, a phase shift, induced as a result of Joule heating, can be observed. For each metal, we measured the sensitivity of the sensor for AC electric current from 0 mA to 35 mA in the coated sensor. The sensitivity of the Au sensor appeared to be about 15.92 degree/mA and of the Ni-Cr sensor, about 39.43 degree/mA. The temperature dependency of the sensor is measured at about 2.41 degree//spl deg/C.