Fast Turn-off Speed Research Articles

On-Chip Active Turn-Off Driving Technique to Prevent Channel Current From Disappearing Prematurely in SiC MOSFET’s Applications

Silicon carbide (SiC) MOSFET has significant advantages in high-voltage (HV) and high-frequency (HF) applications due to its electrical characteristics. In order to make use of its merits, the active driver is necessary for SiC MOSFET. During the turn-off operation of SiC MOSFET, it is critical to prevent the channel current from disappearing prematurely, which has not been addressed in existing active drivers. This brief proposes an on-chip active turn-off driver to realize the fast turn-off speed and low EMI noises. The mechanism is that the turn-off driving current needs to be adjusted rapidly according to the operating state of SiC MOSFET, which can also ensure that EMI noises and overshoots are under control. Then, the proposed turn-off driver is fabricated in a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.18~\mu \text{m}$ </tex-math></inline-formula> BCD process and occupies a 0.99mm2 active area. Finally, using the proposed active turn-off driver, the turn-off operation of SiC MOSFET has experimented with the 15A and 90A load current, respectively. SiC MOSFET realizes a high turn-off performance, about 200ns turn-off time with low EMI noises, demonstrating that the proposed on-chip active turn-off driving technique is suitable for SiC MOSFET under different loads.

Improved Turn-Off Speed and Uniformity of Atomic Threshold Switch Device by AgSe Electrode and Bipolar Pulse Forming

To improve the turn-off speed and uniformity of atomic threshold switching (TS) devices, we propose the use of the AgSe electrode and controlled bipolar pulse forming method. Compared with TS devices with Ag and AgTe electrodes, TS device with the AgSe electrode shows an extremely fast turn-off speed, which can be explained by the limited injection of Ag into the switching layer. By applying positive bias (Icc = 500 nA, 1 ms) followed by negative bias (−0.1 to −0.2 V, $10~\mu \text{s}$ ), the TS device exhibits excellent switching uniformity. It can be explained by the formation of atomic-scale filament under the positive bias at low Icc and drift-back of excessive Ag by the negative bias. By designing the shape of the filament and concentration of the residual Ag, the TS device with the AgSe electrode shows promise for selector applications.

Fabrication and Investigation of a Lateral Insulated Gate-Bipolar-Transistor With Ultrafast Turn-Off Speed

A hole-controlled lateral insulated gate bipolar transistor (HC-LIGBT) device with an ultrafast turn-off speed is investigated and experimentally demonstrated. Utilizing a high-permittivity material as the dielectric on the novel device structure, the hole carrier movements are controlled. In the device ON-state, the anode plasma injection effect is amplified to improve the current density. In the OFF-state, the electrons in the drift region are rapidly neutralized by the hole current, after which the anode voltage is pulled to the bus voltage by the external driving circuit through a voltage couple to realize a fast turn-off speed. The ON-state current is not compromised for the switching speed. The device is fabricated with a 1 μm fully custom process using Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> as the dielectric. The test results indicate that the breakdown voltage of the device is 350 V, the ON-state current density is 155 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at an anode voltage of 2 V, and the rising edge of the voltage on the anode in the turn-off state lasts only 90 ns.

Hybrid Selector With Excellent Selectivity and Fast Switching Speed for X-Point Memory Array

In this letter, we demonstrate a new concept of threshold selector by combining Ag-based selector with NbO x insulator metal transition (IMT) selector. To overcome intrinsic limits of slow turn-off speed ( $> 1\mu \text{s}$ ) of the Ag-based selector, we adopted NbO x IMT selector with fast turn-off speed. The hybrid device exhibits excellent selector characteristics, such as extremely low off-current ( $ ). It shows excellent read-out margin (>75% at >210 word lines) in a fast sequential operation of cross point memory array.

An Ultralow Loss Superjunction Reverse Blocking Insulated-Gate Bipolar Transistor With Shorted-Collector Trench

A novel superjunction (SJ) reverse-blocking (RB) insulated gate bipolar transistor (IGBT) is proposed and investigated for the first time. The device features a shorted collector trench (SCT) at the bottom, an SJ structure in the drift region, and an N1-layer as well as N2-layer at the bottom and top side of N-pillar, respectively. First, the SCT combined with the N2 enables the SJ RB-IGBT to sustain a high reverse breakdown voltage (BV $_{\textit {R}}$ ). The SCT assists in depleting the N1 in the reverse blocking state, enabling a high BV $_{\textit {R}}$ under the condition of a high N1 doping that is required to maintain a high forward breakdown voltage (BV $_{\textit {F}}$ ). The N2 acts as a field-stop layer in the reverse blocking state. Second, unlike the conventional SJ IGBT, the SJ RB-IGBT maintains bipolar conducting mode in the ON-state even with high N/P pillar doping of $6 \times 10^{15}$ cm $^{\mathrm {-3}}$ , due to carrier store effect induced by N2. Thus, a low ON-state voltage ( $\text{V}_{\mathrm{\scriptscriptstyle ON}}$ ) is obtained. Third, the SJ junction extracts the plasma into separate pillars during turn OFF, enabling a fast turn-OFF speed that is comparable with unipolar devices. The SJ RB-IGBT realizes bidirectional blocking capability >1200V and turn-OFF loss 80% lower than that of the state-of-the-art RB-IGBT.

Diamond Schottky-pn diode with high forward current density and fast switching operation

We fabricated a diamond diode, namely a Schottky-pn diode (SPND), which is composed of a fully depleted n-type active layer sandwiched between a highly doped p-type layer and a Schottky metal layer. The SPND has superior characteristics that overcome the weak points of both a Schottky barrier diode and a pn diode. That is, the SPND showed high current density (over 4000 A/cm2) with low specific resistance (0.4 mΩ cm2) at a forward bias of 6 V while maintaining a high rectification ratio of ∼1010. Moreover, the SPND showed extremely fast turn-off speed of nanosecond order.

Transient characteristics of n-channel hybrid Schottky injection FETs

Theoretical transient characteristics of hybrid Schottky injection FETs (HSINFETs) are considered. The theoretical analysis is based on two-dimensional numerical simulations, in which the entire turn-off process and the effects of minority-carrier injection levels on the transient performance of the HSINFET device are analyzed. The analysis shows that the fast turn-off speed in the HSINFET device occurs because (1) only a small number of minority carriers is injected into the drift region, (2) a current path, provided by the Schottky contact, effectively removes electrons from the drift region during turn-off, and (3) Schottky clamping at the anode is effective during turn-off and prevents the p/sup +/ portion of the hybrid anode from significantly injecting holes. Experimental results compared the DC and transient performance of the lateral double-diffused MOS transistor (LDMOST), lateral insulated-gate transistor (LIGT), Schottky injection field-effect (SINFET), and HSINFET are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>