Browsing by Author "Yang, Jiancheng"

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A Reconfigurable, Pulse-shaping Potentiometric Readout System for Bio-Sensing Transistors
(2019-01-01)
Lu, Shao-Yung
;
Shan, Siang-Sin
;
Yang, Jiancheng
;
Chang, Chin-Wei
;
Ren, Fan
This paper presents a new multi-modality readout system for potentiometric electrochemical sensors. The design adopts a pulse modulation at the gate and drain of the Bio-FET sensors to reduce the effects of charge accumulation between the surface of the electrodes and the ion analytes. The adjustable duration and amplitude of stimuli signals provide flexibility for different biosensing applications and a wide range of detectable concentration. Also, an oscillator-based architecture is proposed for digitization and integration. The counting time can be adjusted to enhance the resolution of the readout system. The proposed potentiometric sensing system was tested with 0.1-10 mM Potassium Ferricyanide (K-3[Fe(CN)(6)]), and the results are interpreted in the micro-LCD on the board. The design offers the opportunity for a handheld medical device with fast and real-time monitoring of biomarkers and ion analytes.
DC and dynamic switching characteristics of field-plated vertical geometry beta-Ga2O3 rectifiers
(2019-01-01)
Yang, Jiancheng
;
Carey, Patrick
;
Ren, Fan
;
Chen, Yen-Ting
;
Liao, Y.
Reverse breakdown voltages larger than 1 kV have been reported for both unterminated Ga2O3 vertical rectifiers (1000-1600 V) and field-plated Schottky diodes (1076-2300 V) with an epi thickness of 8-20 mu m. If the doping is in the 10(16) cm range, the breakdown is usually in the 500-800V regime. Furthermore, the switching characteristics of discrete Ga2O3 vertical Schottky rectifiers exhibited reverse recovery times in the range of 20 to 30 ns. Large area (up to 0.2 cm(2)) Ga2O3 rectifiers were fabricated on a Si-doped n-Ga2O3 drift layer grown by halide vapor phase epitaxy on a Sn-doped n(+) Ga2O3 (001) substrate. A forward current of 2.2 A was achieved in single-sweep voltage mode, a record for Ga2O3 rectifiers. The on-state resistance was 0.26 Omega.cm(2) for these largest diodes, decreasing to 5.9 x 10 Omega.cm(2) for 40x40 mu m devices. We detail the design and fabrication of these devices. In addition, an inductive load test circuit was used to measure the switching performance of field-plated, edge-terminated Schottky rectifiers with a reverse breakdown voltage of 760 V (0.1 cm diameter, 7.85 x10(-3) cm(2) area) and an absolute forward current of 1 A on 8 mu m thick epitaxial beta-Ga2O3 drift layers. These devices were switched from 0.225 A to -700 V with t of 82 ns, and from 1 A to -300 V with t of 64 ns and no significant temperature dependence up to 125 degrees C. There was no significant temperature dependence of t(rr)up to 150 degrees C.
Dynamic Switching Characteristics of 1 A Forward Current beta-Ga2O3 Rectifiers
(2019-01-01)
Yang, Jiancheng
;
Ren, Fan
;
Chen, Yen-Ting
;
Liao, Yu-Te
;
Chang, Chin-Wei
An inductive load test circuit was used to measure the switching performance of field-plated edge-terminated Schottky rectifiers with a reverse breakdown voltage of 760 V (0.1 cm diameter, 7.85 x 10(-3) cm(2) area) and an absolute forward current of 1 A on 8 mu m thick epitaxial beta-Ga2O3 drift layers. The recovery characteristics for these vertical geometry beta-Ga2O3 Schottky rectifiers switching from forward current of 1 A to reverse off-state voltage of -300 V showed a recovery time (trr) of 64 ns. There was no significant temperature dependence of trr up to 150 degrees C.
Implementation of a 900 V Switching Circuit for High Breakdown Voltage beta-Ga2O3 Schottky Diodes
(2019-05-22)
Chen, Yen-Ting
;
Yang, Jiancheng
;
Ren, Fan
;
Chang, Chin-Wei
;
Lin, Jenshan
This paper presents a switching circuit for high breakdown-voltage Ga2O3 vertical Schottky rectifiers. Field-plated edge-terminated (FPET) vertical Schottky diodes were fabricated on a 20-mu m thick Si-doped n-type Ga2O3 drift layer which was grown on the 650-mu m thick beta-Ga2O3 substrate via halide vapor phase epitaxy (HVPE). The measured reverse recovery time of the proposed Ga2O3 Schottky diode was 81 ns when switched to a reverse bias voltage of -900 V. The implementation of a switching circuit with the novel Ga2O3 diode is the first demonstrated at such a high switching voltage. This paper also provides insights for the practical implementation of the Ga2O3 vertical Schottky rectifiers from device fabrication to circuit design. (C) The Author(s) 2019. Published by ECS.
Switching Behavior and Forward Bias Degradation of 700V, 0.2A, beta-Ga2O3 Vertical Geometry Rectifiers
(2019-01-30)
Yang, Jiancheng
;
Fares, Chaker
;
Ren, Fan
;
Chen, Yen-Ting
;
Liao, Yu-Te
We report the switching recovery characteristics of large area (contact dimension 0.04 x 0.04 cm(2)) vertical geometry beta-Ga2O3 Schottky rectifiers, consisting of Si-doped epitaxial layers on conducting bulk substrates. Devices that were switched from forward current of 0.225 A to reverse off-state voltage of -700 V in an inductive load test circuit showed a recovery time (t(rr)) of 82 ns, with a reverse recovery current (I-rr) of 38 mA and dI/dt of -2.28 A. mu sec(-1). This shows the potential of Ga2O3 rectifiers for power switching applications, provided effective thermal management schemes can be implemented. Devices deliberately tested to failure under forward bias conditions exhibit delamination and cracking of the Ni/Au contact and underlying epitaxial Ga2O3 due to the low thermal conductivity of the Ga2O3. This failure mode is different to that under high reverse breakdown conditions, where pits formed by material failure under the high field generated at the edge of the rectifying contact occurs. (C) The Author(s) 2019. Published by ECS.