Medium Voltage Nitride Power Switches Enabled by Vertical Superjunction Technology (21-000000002)
Abstract
Low-cost, efficient, fast, and reliable power devices that work at high-frequencies and high-voltage levels are central to improving the efficiency of electrical energy processing. Medium-voltage power devices (1 kV-35 kV) are widely used in applications such as electric ships, power plants, electrical grid, industrial motor drives, etc. For example, 1.2 kV-to-10 kV power devices are greatly needed in the Power Electronics Building Block (PEBB) under development for the future applications in naval shipboard power systems. Today s medium-voltage power devices are mainly made of silicon (Si) and silicon carbide (SiC), while gallium nitride (GaN)-based devices are widely perceived as excellent candidates for the next-generation of high-frequency medium-voltage applications, owing tothe superior physical properties of GaN compared to Si and SiC. One of the main objectives in the design of power devices is to obtain a high off-state breakdown voltage while minimizing the on-state resistance. Power devices are limited by the trade-off between breakdown voltage and on-resistance. A vertical superjunction device, which consists of alternative p-type and n-type pillars, couldbreak the theoretical limit of conventional 1-D power devices, and achieve over 10-fold lower specific on-resistance than conventional power devices for the same breakdown voltage, at the same time that the capacitances and charges are significantly reduced, allowing for a megahertz switching frequency in kilovolts switching, and the material cost can be also reduced. However, no GaN vertical superjunction devices have been demonstrated so far due to scientific knowledge gaps and technical challenges in material growth and device fabrication.In this five-year project, Virginia Tech (VT), working with Qorvo, will pursue coordinated efforts to realize the medium-voltage vertical GaN superjunction technologies. This will initially focus on the demonstration of 1.2-1.7 kV prototypes,then scaling to 3.3-10 kV. Two technical approaches will be pursued to fabricate vertical GaN superjunction: (a) trench technology,i.e., formation of deep trenches and subsequent epitaxial filling of compensating pillars; (b) multi-epitaxy technology, i.e., multiple steps of masked implantation and epitaxial growth to make the n- and p-pillars. The VT team performs device design, modeling, simulation, fabrication and characterization; The Qorvo team offers support on p-type GaN regrowth and activation in the trench technology. This team will also participate in the GaN Superjunction working group established by the U.S. Naval Research Laboratory (NRL). Specific collaborations will include a joint effort with NRL to develop the multi-epitaxy approach utilizing their expertise in p-type dopant activation and epitaxial regrowth, as well as obtain thick drift layers with low background impurity utilizing their state-of-the-art GaN metal organic chemical vapor deposition (MOCVD) reactors; joint studies with Penn State University will also be performed to understanding processes, defects and interfaces that are common to both the lateral and vertical GaN superjunction structures.This work, if successful, will significantly extend the application space of GaN devices, enable an unprecedented level of miniaturization and integration of medium-voltage power electronics, lower the energy loss in power applications, and foster the increased adoption of power electronics in naval shipboard power systems.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 06, 2021
- Source ID
- N000142112183
Entities
People
- Yuhao Zhang
Organizations
- Office of Naval Research
- United States Navy
- Virginia Tech