Papers by Keyword: Diode

Abstract: In the last decades, silicon carbide (SiC) based heterostructures have gained a remarkable place in research field due to their exceptional properties. These properties make SiC highly suitable for high temperature, high frequency, and high power electronics applications. The most prominent polytypes (among 200 types) of SiC like 3C-SiC, 4H-SiC and 6H-SiC, have distinctive electrical and physical attributes that make them promising candidates for high performance optoelectronic applications. Silicon (Si) also has been accepted as a promising material for wide range of electronic, optical and optoelectronic applications. Heterostructures fabricated by the direct bonding of SiC polytype and Si may have interesting physical and electrical attributes. In this paper, micro and nano-scale simulations of the nn-heterostructures of Si/4H-SiC and Si/3C-SiC have been done with Silvaco TCAD and QuantumWise Atomistix Toolkit (ATK) softwares respectively. Voltage-current density characteristics of the nanoscale and microscale simulated devices are computed and discussed. In nanoscale devices, the effects of defects due to lattice misplacements (axial displacement of bonded wafers) are also studied. These simulations are the preparation for our future experiments, which are targeted to produce either a high electron mobility diode or a light emitting diode, by direct bonding (diffusion welding) of SiC polytypes.

Abstract: Silicon Carbide JBS diodes are capable, in forward bias, of carrying surge current of magnitude significantly higher than their rated current, for short periods. In this work, we examine the mechanisms of device failure due to excess surge current by analyzing variation of failure current with device current and voltage ratings, as well as duration of current surge. Physical failure analysis is carried out to correlate to electrical failure signature. We also quantify the impact, on surge current capability, of the resistance of the anode ohmic contact to the p-shielding region.

Abstract: Wide-bandgap power semiconductor devices offer enormous energy efficiency gains in a wide range of potential applications. As silicon-based semiconductors are fast approaching their performance limits for high power requirements, wide-bandgap semiconductors such as gallium nitride (GaN) and silicon carbide (SiC) with their superior electrical properties are likely candidates to replace silicon in the near future. Along with higher blocking voltages wide-bandgap semiconductors offer breakthrough relative circuit performance enabling low losses, high switching frequencies, and high temperature operation. ARPA-E’s SWITCHES program, started in 2014, set out to catalyze the development of vertical GaN devices using innovations in materials and device architectures to achieve three key aggressive targets: 1200V breakdown voltage (BV), 100A single-die diode and transistor current, and a packaged device cost of no more than ȼ10/A. The program is drawing to a close by the end of 2017 and while no individual project has yet to achieve all the targets of the program, they have made tremendous advances and technical breakthroughs in vertical device architecture and materials development. GaN crystals have been grown by the ammonothermal technique and 2-inch GaN wafers have been fabricated from them. Near theoretical, high-voltage (1700-4000V) and high current (up to 400A pulsed) vertical GaN diodes have been demonstrated along with innovative vertical GaN transistor structures capable of high voltage (800-1500V) and low R_ON (0.36-2.6 mΩ-cm2). The challenge of selective area doping, needed in order to move to higher voltage transistor devices has been identified. Furthermore, a roadmap has been developed that will allow high voltage/current vertical GaN devices to reach ȼ5/A to ȼ7/A, realizing functional cost parity with high voltage silicon power transistors.

Abstract: In this work, >2kV PiN diodes with >10um deep implant of B⁺ and 6um deep implant of Al⁺ have been fabricated to evaluate the quality of resulting pn junction after high-energy implantation. Acceptable low leakage currents at reverse bias and stable avalanche breakdown were observed for high energy implanted diodes (HEI-diodes) when compared to No-HEI-diodes that suggests minimal defect sites present after activation anneal.

Abstract: The incorporation of Germanium (Ge) in 4H-SiC has recently being reported as enabling an increase of the electron mobility in n-type doped layers. The present work aims at evaluating the impact of the Ge doping on two types of SiC devices: Merged PiN-Schottky (MPS) diodes and Trench MOSFETs.

Abstract: Reliability characterization of SiC devices is an ongoing activity. For this work, 650 V SiC JBS diodes in TO247 housings were tested in H3TRB. After a test period of 4000 hours none of the devices had failed during the test and only two out of sixteen devices had failed during blocking curve measurements performed at intermediate time steps. This is significantly better performance than many silicon devices offer today. The failure spots of the failed devices were detected at the edge of the main junction appearing as semi-circular cavities in the aluminum metallization. All other devices did not even show deviations from their original blocking curves.

Abstract: Using a combination of photoluminescence and electrical characterization, defects in the epitaxial layer of unipolar 4H-SiC power devices were matched to device characteristics and statistically analyzed. In-grown triangles had no significant effect on diode and VDMOS blocking or conduction mode, while surface triangles lead to high leakage currents even below 1 V reverse bias.

Abstract: High-energy neutrons produced by cosmic ray interactions with our atmosphere are known to cause single-event burnout (SEB) failure in power devices operating at high fields. We have performed accelerated high-energy neutron SEB testing of SiC and Si power devices at the Los Alamos Neutron Science Center (LANCSE). Comparing Wolfspeed SiC MOSFETs having different voltage (900V – 3300V) and current (3.5A – 72A) ratings, we find a universal behavior when scaling failure rates by active area, and scaling drain bias by avalanche voltage. Moreover, diodes and MOSFETs behave similarly, revealing that the SiC drift dominates the failure characteristics for both device types. This universal scaling holds for SiC MOSFETs from other manufacturers as well. The SEB characteristics of Si power IGBT and MOSFET devices show that near their rated voltages failure rates of Si devices can be 10X higher than that of comparable SiC MOSFET devices. Thus, Si devices are more susceptible to SEB failure from voltage overshoot conditions.

Abstract: We report on the development of a new generation of SiC Schottky rectifier devices employing a Molybdenum based barrier metal system and a new stripe cell design for field shielding and optimized area utilization. The Schottky barrier height is reduced and thus the conduction losses are decreased significantly. The balance between forward conduction and reverse leakage losses as well as the homogeneity and stability of the new barrier system are investigated carefully.

Abstract: Wide bandgap semiconductors, such as 4H SiC, are suitable for power regulating devices, due to compatibility with conventional process integration, high breakdown voltage and thermal conductivity [1]. For RF applications, in order to achieve better switching speed, high cut off frequency, and low series resistance (Rdson), it is essential to choose the right gate metals [2]. Engineering of the gate metals not only improves the critical device parameters by adjustment of the metal workfunction, but also affects how the high aspect ratio trenches are filled for a next generation SIT device configuration [3] - [5].