Soo-Seong Kim

High breakdown voltage GaN Schottky barrier diode employing floating metal rings on AlGaN/GaN hetero-junction

We have reported a lateral GaN SBDs on AlGaN/GaN hetero-junction employing floating metal rings (FMRs) which exhibit a very high breakdown voltage, a low leakage current and a low on-state voltage. We have obtained a very high breakdown voltage of 930V without any additional process step. We have also optimized design parameters of FMR, such as the space between main junction and FMR and the number of rings. Our experimental results show that FMR which is rather simple may be suitable for lateral GaN SBD.

A new vertical GaN Schottky barrier diode with floating metal ring for high breakdown voltage

A vertical GaN Schottky barrier diode (SBD) employing a floating metal ring as an edge termination is described. The breakdown voltage is larger than a device without any termination that has been fabricated on a bulk GaN substrate. Fabricated GaN SBD exhibits a high breakdown voltage of 353 V and very fast reverse recovery characteristics of 28 ns. The breakdown voltage of a device without termination is 159 V. It should be noted that the proposed device does not require any additional processes.

Measurement of the refractive index of the LAB-based liquid scintillator and acrylic at RENO

In this paper, we describe the first measurement of the refractive index of the linear alkyl benzene (LAB)-based liquid scintillator and acrylic used at the Reactor Experiment for Neutrino Oscillation (RENO). The refractive index of a material is an important optical property and the prism spectrometer is the most common device for measuring the refractive index. Using the minimum deviation technique, which requires an exact measurement of the apex angle, we determined the refractive indices at six different wavelengths and then fitted them. We also compared the refractive index of the LAB-based liquid scintillator with the refractive indices of other liquid scintillator solvents commonly used in reactor neutrino experiments.

A New Trenched Source Power MOSFET Improving Avalanche Energy

A new power metal oxide semiconductor field effect transistor (MOSFET) with a deep body contact, which improves the avalanche energy capability, is proposed and verified by the 2D numerical simulation. The deep body contact employing the trench process alters the direction of the current flow from the edge to the bottom of the p-body under the unclamped inductive switching (UIS) condition. The deep body contact also suppresses the activation of the parasitic bipolar transistor due to the reduction of the current density beneath the n+ source. The ruggedness of the proposed power MOSFET is improved without sacrificing any other electrical characteristics and increasing device area.

A new fault protection circuit of 600V PT-IGBT for the improved avalanche energy employing the floating p-well

A fault protection circuit, which detects over-voltage under short circuit fault, of IGBT for the improved undamped inductive switching (UIS) capability using floating p-well is proposed and fabricated. Experimental results show that the proposed circuit successfully exhibits the reduction of collector current under fault condition when the protection circuit detects the fault signal and immediately lowers gate voltage. We have also verified the operation of the proposed circuit and device by employing the measurement under hard switching fault (HSF) and fault under load (FUL) conditions and two-dimensional mixed-mode simulation.

A new protection circuit for high-voltage current saturation of LEST

A new protection circuit for high-voltage current saturation of a lateral emitter switched thyristor (LEST) is proposed. We fabricated this circuit by employing a widely used insulated gate bipolar transistor compatible process. A high-voltage current saturation exceeding 200 V was measured in the EST with the proposed protection circuit, while the current saturation of the conventional LEST is limited to 17 V by the breakdown of the lateral MOSFET.

A new 600V PT-IGBT for the improved avalanche energy by employing the floating p-well

A new IGBT employing a floating p-well, which improves the avalanche energy, is proposed and verified using the 2D numerical simulation. By implementing the floating p-well, the peak point of impact ionization moves from the surface under the gate to the bottom of the p-well so that the hole current flows vertically through the bottom of the p-well under the unclamped inductive switching (UIS). Hence, the avalanche capability can be significantly improved by the reduction of the hole current beneath the n+ emitter. Also, the saturation voltage of the proposed device can be comparable to that of the conventional device by adjusting the thickness of the n-epitaxial layer.

Experimental Study on Improving Unclamped Inductive Switching Characteristics of the New Power Metal Oxide Semiconductor Field Effect Transistor Employing Deep Body Contact

A new power metal oxide semiconductor field effect transistor (MOSFET) with deep body contact (DBC), which improves the avalanche energy capability, is proposed and verified by experimental results. For the experiment, a 60 V, 1 A power MOSFET employing DBC has been fabricated using a complementary metal oxide semiconductor (CMOS) compatible deep Si trench process. Previous simulations show that DBC alters the direction of the current flow from the edge to the bottom of the p-body under unclamped inductive switching (UIS) conditions. DBC also suppresses the activation of the parasitic bipolar transistor due to the reduction of the current density beneath the n+ source. Experimental results show that the ruggedness of the proposed power MOSFET is improved without sacrificing any other electrical characteristics and increasing device area.

Trench Insulated Gate Bipolar Transistor for the Improved Short Circuit Capability Employing Curved Junction and Wide Cell Pitch

A trench insulated gate bipolar transistor (IGBT) employing the curved p-well junction and wide cell pitch, which improves the short circuit capability, is proposed and verified by the 2D numerical simulation. The wide cell pitch improves the short circuit immunity of the proposed IGBT due to the reduced current level under the short circuit condition. The curved p-well junction and the carrier stored layer (CSL) move the highly resistive region toward the surface so that the saturation voltage of the proposed IGBT is slightly higher than that of the conventional IGBT. The short circuit withstanding time of the proposed IGBT is 2.4 times higher than that of the conventional one without any increase of the conduction loss.

A new lateral anode switched thyristor (LAST) with current saturation and low turn-off time

A novel MOS-gate controlled thyristor, entitled lateral anode switched thyristor (LAST), which exhibits a high current saturation and a low turn-off time, is proposed and successfully fabricated. Experimental results show that the new LAST achieves a current saturation capability larger than 1200 A/cm/sup 2/ even at high anode voltages. The forward voltage drop of LAST is 1.2 V at 100 A/cm/sup 2/ where 10 V was biased to the dual gates. The turn-off time of LAST without any lifetime-control process is 1.5 /spl mu/s while that of LAST without p/sup +/ diverter is about 2.9 /spl mu/s. Our experimental data indicates that the p/sup +/ diverter successfully diverts holes in the drift region during the turn-off and a turn-off time is considerably decreased in the proposed LAST. The LAST, where any trouble-some parasitic thyristor mechanism is eliminated, completely suppresses a latch-up and increases the maximum controllable current considerably.