Temperature-Dependent Characteristics of 4H-SiC Buried Grid JBS Diodes

The Junction Barrier Schottky (JBS) diode in silicon carbide is a promising candidate for a low-leakage power rectifier for high switching frequencies and elevated temperature operation. It has the advantage of a low forward voltage drop while keeping a low leakage current at high blocking voltage. JBS devices have been fabricated in 4H SiC and 6H SiC and then electrically characterised in comparison with pn and Schottky diodes on the same wafer. The JBS devices reached blocking voltages up to 1.0 kV at a leakage current density of 13 IŒA/cm2 and the forward conduction was limited by an on-resistance close to the theoretical value.

A 2-dimensional fully analytical model for design of high voltage junction barrier Schottky (JBS) diodes

A physics based compact model for SiC Junction Barrier Schottky (JBS) diodes is presented which features a comprehensive physical description of the DC and CV behavior of SiC JBS diodes. For the first time, modeling of leakage current for JBS diode in circuit simulation is done. The model includes temperature scaling of its parameters to enable modeling of the diodes over a wide range of temperature (25 °C to 175 °C). The model has been validated using characterization data from a 1200 V, 3 A SiC JBS diode from GeneSiC. Excellent agreement is shown between device measurements and simulation for all regimes of operation of the diode.

This paper reports the detailed design, fabrication, and characterization of two sets of high-power 4H-silicon carbide (4H-SiC) junction barrier Schottky (JBS) diodes - one with a 1500-V, 4-A capability and another with 1410-V, 20-A capability. Two-dimensional (2-D) device simulations show that a grid spacing of 4 /spl mu/m results in the most optimum trade-off between the on-state and off-state characteristics for these device ratings. JBS diodes with linear and honeycombed p/sup +/ grids, Schottky diodes and implanted p-i-n diodes fabricated alongside show that while 4H-SiC JBS diodes behave similar to,Schottky diodes in the on-state and switching characteristics, they show reverse characteristics similar to p-i-n diodes. Measurements on 4H-SiC JBS diodes indicate that the reverse-recovery time (/spl tau//sub rr/) and associated losses are near-zero even at a high reverse dI/dt of 75 A//spl mu/s. A dc/dc converter efficiency improvement of 3-6% was obtained over the fastest, lower blocking voltage silicon (Si) diode when operated in the 100-200 kHz range.

Various layouts of the anode of Junction Barrier Schottky (JBS) diodes are compared theoretically and it is found that the hexagonal honeycomb structure with 3-D symmetry offers the best figure of merit (FOM). Proportional relationships between the various layouts are reported, using which we extend a fully analytical 2-D model for reverse biased field shielding in a JBS diode to the superior 3-D layouts. The effect of reducing implanted feature size is also analyzed as a trade-off between FOM and breakdown voltage capability.

High-performance gallium oxide (Ga2O3) junction barrier Schottky (JBS) diodes were fabricated using planar and trench junction barrier designs. Their electrical transport mechanisms were systematically studied. The JBS integration strengthens interfacial depletion via p–n junction-induced Ga2O3 conduction band elevation, whereas the trench design forms a higher interfacial barrier and expands lateral depletion, effectively modulating carrier transport. Additionally, the JBS structure reduces the electric field at the Schottky interface which not only suppresses Schottky barrier lowering to reduce reverse leakage current but also mitigates surface field crowding to prevent premature device breakdown. The forward current density ratios of Schottky barrier diodes (SBDs) with a JBS reached an impressive 8.0 × 1010, demonstrating exceptional switching characteristics. The reverse breakdown voltage of the SBDs with trench JBS increases from 310 V in the SBDs to a remarkable 1150 V, representing roughly a 3.7-time. The leakage current is simultaneously reduced by two orders of magnitude to an ultra-low value of 1.1 × 10−9 A cm−2. A comparative analysis of device performance between planar and trench JBS structures is presented, offering a theoretical foundation and reference for future innovations in Ga2O3-based SBDs.

It is known that a Schottky barrier height (b) of metal/C-face 4H-SiC Schottky barrier diode (SBD) differ from b of metal/Si-face 4H-SiC SBD. Furthermore, b of metal/4H-SiC SBD varies with annealing temperature. We fabricate 0.231mm2 SBD with Ti/SiC interface using Si-face and C-face 4H-SiC. These SBDs are annealed at several temperatures after a formation of the Ti/SiC interface. As a result, b of Ti/C-face 4H-SiC interface annealed at 400 oC is nearly equal to b of Ti/Si-face 4H-SiC interface annealed at 500 oC and the n-values of these SBDs are nearly equal to the ideal value (unity). Using that annealing condition, we fabricated 25mm2 junction barrier Schottky (JBS) diodes with Ti/SiC interface on Si-face and C-face 4H-SiC epitaxial substrate. b of Si-face and C-face JBS diodes are 1.26eV and 1.24eV, respectively. The leakage currents for both Si-face and C-face JBS diodes are less than 1mA/cm2. The current of 100A is obtained at the forward bias voltage of 1.95V and 2.16V for the Si-face JBS and the C-face JBS.

Silicon carbide (SiC) junction barrier Schottky (JBS) diode has been widely used in power electronic systems due to its excellent physical characteristics and electrical performance, and the structural design of its source area has a particularly significant impact on the performance. This study provides a comparative analysis of the SiC JBS diode performance of different hexagonal structures, aiming to provide theoretical support and practical guidance for the optimization of JBS diode performance. Through theoretical derivation, experimental verification and data processing, the paper deeply analyzes the influence of hexagonal structure on JBS diode current distribution and breakdown voltage, and proposes a targeted optimization strategy.

4H-SiC junction barrier Schottky (JBS) diodes with four kinds of design have been fabricated and characterized using two different processes in which one is fabricated by making the P-type ohmic contact of the anode independently, and the other is processed by depositing a Schottky metal multi-layer on the whole anode. The reverse performances are compared to find the influences of these factors. The results show that JBS diodes with field guard rings have a lower reverse current density and a higher breakdown voltage, and with independent P-type ohmic contact manufacturing, the reverse performance of 4H-SiC JBS diodes can be improved effectively. Furthermore, the P-type ohmic contact is studied in this work.

This work explores the effects of extended epitaxial defects on 4H-SiC power devices. Advanced defect mapping techniques were used on large quantities of power device wafers, and data was aggregated to correlate device electrical characteristics to defect content. 1200 V class Junction Barrier Schottky (JBS) diodes and MOSFETs were examined in this manner; higher voltage 3.3 kV class devices were examined as well. 3C inclusions and triangular defects, as well as heavily decorated substrate scratches, were found to be device killing defects. Other defects were found to have negligible impacts on device yield, even in the case of extremely high threading dislocation content. Defect impacts on device reliability was explored on MOS-gate structures, as well as long-term device blocking tests on both MOSFETs and JBS diodes. Devices that passed on-wafer electrical parametric tests were found to operate reliably in these tests, regardless of defect content.

The static and dynamic characteristics of 13-kV class 4H-SiC junction barrier Schottky (JBS) diodes with a three-zone junction termination extension (JTE) are presented. Using an anisotropy breakdown model, technology computer-aided design simulation of devices with a three-zone JTE agrees well with the obtained experimental results, correctly predicting a sharp drop in blocking voltage at high JTE acceptor concentrations. The forward voltage of the JBS diode at 75°C and a forward current of 500 mA is reduced to approximately one-ninth by that of 13 series-connected 1000-V Si PiN diodes. This suggests that conduction losses of traditional high-voltage circuits which conventionally use series-connected devices can be drastically reduced by replacing the series-connected devices with a single 13-kV class SiC JBS diode. Moreover, the reverse recovery current waveform of the 13-kV class SiC JBS diode shows that these diodes have lower reverse recovery losses than a 13-kV SiC PiN diode.

Power electronic devices are crucial components of power converter systems. The evolution of power devices drives the development of power converters, including improvements in performance, reliability, and power capacity. In this chapter, the author expounds the structure, working principle, and static and dynamic characteristics of the conventional PN junction diode. And the silicon carbide (SiC) Schottky barrier diode (SBD), junction barrier Schottky (JBS) diode, trench JBS (T-JBS) diode, and sidewall-enhanced trench JBS (SET-JBS) diode are also discussed and compared. Also, the structures and properties of the gallium oxide (Ga2O3) SBD and heterojunction diode are also summarized. Next, the author gives a detailed analysis and discussion of the silicon power metal-oxide-semiconductor field-effect transistor (MOSFET), superjunction MOSFET, and the SiC MOSFET and JFET, and the Ga2O3 MOSFET. Then, the device structure and operating principle, switching characteristics, and current tailing mechanism of the insulated gate bipolar transistor (IGBT) are also analyzed and summarized in detail. Finally, the energy band structure, working principle, and switching characteristic of the gallium nitride (GaN) high-electron mobility transistor (HEMT), one of the hot devices in the current market, are also described. Finally, the summary and prospect of power electronic devices are also presented in this chapter.

A comprehensive investigation was conducted to explore the degradation mechanism of leakage current in SiC junction barrier Schottky (JBS) diodes under heavy ion irradiation. We propose and verify that the generation of stacking faults (SFs) induced by the recombination of massive electron--hole pairs during irradiation is the cause of reverse leakage current degradation based on experiments results. The irradiation experiment was carried out based on Ta ions with high linear energy transfer (LET) of 90.5 MeV/(mg/cm2). It is observed that the leakage current of the diode undergoes the permanent increase during irradiation when biased at 20% of the rated reverse voltage. Micro-PL spectroscopy and PL micro-imaging were utilized to detect the presence of SFs in the irradiated SiC JBS diodes. We combined the degraded performance of irradiated samples with SFs introduced by heavy ion irradiation. Finally, three-dimensional (3D) TCAD simulation was employed to evaluate the excessive electron–hole pairs (EHPs) concentration excited by heavy ion irradiation. It was observed that the excessive hole concentration under irradiation exceeded significantly the threshold hole concentration necessary for the expansion of SFs in the substrate. The proposed mechanism suggests that the process and material characteristics of the silicon carbide should be considered in order to reinforcing against the single event effect of SiC power devices.

The performance of Junction Barrier Schottky (JBS) diodes developed for medium voltage hard-switched Naval power conversion is reported. Nominally 60 A, 4.5kV rated JBS freewheeling diodes were paired with similarly rated Si IGBTs and evaluated for temperature dependent static and dynamic characteristics as well as HTRB and surge capability. The SiC JBS/Si IGBT pair was also directly compared to Si PiN diode/Si IGBT with similar ratings. Compared to Si, the SiC freewheeling diode produced over twenty times lower reverse recovery charge leading to approximately a factor-of-four-reduction in turn-on loss. Alternatively, for equivalent total switching loss, the SiC JBS/Si IGBT hybrid configuration allows for at least a 50% increase in specific switched power density. Reliability testing showed the devices to be robust with zero failures.

Vertical GaN junction barrier Schottky (JBS) diodes are demonstrated. The JBS p-type grid was formed by Mg-implantation into a 10 μm thick unintentionally doped GaN homoepitaxial drift layer, grown by metal organic chemical vapor deposition (MOCVD). Then, symmetrical multi-cycle rapid thermal annealing (SMRTA) repaired implantation damage and activated the Mg ions. This process includes deposition of an AlN capping layer, annealing in a nitrogen overpressure, and rapid heating and cooling pulsed annealing. In addition, PiN diodes and Schottky barrier diodes (SBDs) were fabricated on the same substrate for comparison. The JBS diode demonstrates forward conduction characteristics dominated by the Schottky barrier (turn-on voltage ∼0.5 V), and reverse breakdown voltage comparable to the PiN diode (−610 V).