OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Microelectronics; Advanced Materials; Hypersonics; Space Technology The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. OBJECTIVE: The objective is to develop extreme environment compatible power converters that use vertical field-effect transistors developed using Ultra-Wide Band Gap (UWBG) material -Ga2O3. Fabrication devices with multi-kilo-volt breakdown voltage made on 4 wafers with high uniformity, radiation hardness, and > 300 C temperature compatibility such that the devices enable extreme environment envelop tracking in radio frequency (RF) amplifiers, pulsed RF communication, and pulsed laser diode applications will be the goal of this SBIR. DESCRIPTION: Radiation-tolerant and high temperature compatible point-of-load (POL) converters are required for Low Earth Orbit (LEO) and hypersonic applications. In current applications, operating voltage of POL converter is significantly derated to reduce single event burnout (SEB) failure. Systems are also designed to reduce the thermal budget for devices by using thermal insulation, active cooling, or by placing devices in low temperature locations. Commercial radiation-hard POL converters are compatible for operation at temperatures significantly below 200 C and are made with low bandgap materials such as Si that can withstand a small breakdown electric field. In comparison, devices made with wider bandgap materials such as Silicon Carbide (SiC), Gallium Nitride (GaN), Gallium Oxide ( -Ga2O3) are expected to have better radiation hardness [1] and higher temperature compatibility [2] compared to Si and therefore are considered for space and defense systems. Wide or Ultra-Wide bandgap-based power converters (compared to smaller bandgap devices) also offer significant SWaP (Size, Weight and Power) advantage for LEO applications. This SBIR requires performers to develop radiation-hard POL converters operating at high voltages and temperatures and responding to MHz input excitation are critical for enabling envelope tracking in RF amplifiers, pulsed RF communication, and pulsed laser diodes. These devices need to have the ability to block high voltages in their OFF state, while operating at a high current and low voltage in ON state therefore, do not have the self-heating (or thermal conductivity) concerns when the system/package is appropriately designed [3]. High critical field strength (Ecrit), high operating temperature, radiation hardness available in UWBG materials are therefore key material's parameters for designing extreme environment POL converters. Among UWBG family, only -Ga2O3 has shallow dopants and can be grown from melt at diameters up to 6 inches. Devices made with -Ga2O3, therefore, offer the potential for a cost-effective, wafer-scale prototyping solution [4]. Lateral devices have already been made using -Ga2O3 in wafer scale, which are relevant for monolithic integration of -Ga2O3 devices in an electronic system. Vertical devices are however preferable for POL converters operated at high current using a smaller footprint as required for the RF applications mentioned above [5-7]. The processing and device fabrication of vertical devices however will require materials and engineering solutions, in terms of large-scale epitaxial growth, controlled ion implantation and etching, high-quality dielectric integration, etc. Characterization of these devices will also require access to radiation and high temperature test facilities available in DoD laboratories and FFRDCs (Federally Funded Research and Development Centers). The performers are recommended to address the regulatory and legal challenges associated with SBIR, provide a comprehensive timeline, and outline a detailed transition and commercialization plan. The performers are also recommended to specify technology readiness levels (TRLs) at the beginning and end of different phases. Appropriate TRL identification will ensure feasibility within the Phase I scope, enhancing credibility and potential for successful implementation in space and hypersonic applications. PHASE I: Under the Phase I effort, the selected performers will demonstrate the capability to fabricate vertical -Ga2O3 transistors and Schottky-barrier diodes (SBDs) in a facility. The performers will also study the extreme environment compatibility of their devices and offer potential solutions. These solutions will address all aspects of vertical device fabrication challenges needed to fabricate a multi-kV, low-loss, high pulsating current device with low specific on resistance equivalent to or better than that of similarly rated commercial devices. The projected device performance can be supported with a technology computer-aided design (TCAD) of the device exposed to radiation. PHASE II: Eligibility for direct to Phase II (D2P2) is predicated on the performer having accomplished a Phase I-like effort predominantly separate from the SBIR Programs. Under the phase II effort, the performer shall sufficiently develop the technical approach, or process to conduct a 4-inch wafer-scale device demonstration and characterize them in extreme environments. Identification of manufacturing/production issues and or business model modifications required to further improve the process and device performance should be documented. These Phase II awards are intended to provide a path to commercialization, not the final step for the proposed solution. PHASE III DUAL USE APPLICATIONS: The performer will demonstrate multi-kV, high-speed, radiation hard, and > 300 C compatible power converter by integrating vertical transistors and SBDs made with -Ga2O3. The converter shall have power-loss comparable to a similarly rated SiC based converter. The performer may pursue commercialization of the various technologies developed in Phase II for transitioning expanded mission capability to a broad range of potential government and civilian users (at AFRL/RQQE and AFRL/RYD) and alternate mission applications. Direct access with end users and government customers (requiring multi-kV converters) will be provided with opportunities to receive Phase III awards for providing the government additional research, development, or direct procurement of products and services developed in coordination with the program. REFERENCES: 1. Reed, F. Kyle, Goetz, K. Callie, Ericson, M. Nance, Sweeney, Daniel C., & Bull Ezell, N. Dianne. Wide Bandgap Semiconductors for Extreme Temperature and Radiation Environments. United States. https://doi.org/10.2172/1856704. 2. P. G. Neudeck, R. S. Okojie, and C. Liang-Yu, "High-temperature electronics - a role for wide bandgap semiconductors?," Proceedings of the IEEE, vol. 90, no. 6, pp. 1065-1076, 2002. 3. L. Boteler, A. Lelis, M. Berman and M. Fish, "Thermal Conductivity of Power Semiconductors When Does It Matter?," 2019 IEEE 7th Workshop on Wide Bandgap Power Devices and Applications (WiPDA), Raleigh, NC, USA, 2019, pp. 265-271, doi: 10.1109/WiPDA46397.2019.8998802. 4. G. Jessen, Gallium Oxide: The Supercharged Semiconductor , IEEE Spectrum, May 2021; A. J. Green et al., APL Materials, 2022, 029201. 5. C. Arnaud, et al., "An active pulsed RF and pulsed DC load-pull system for the characterization of HBT power amplifiers used in coherent radar and communication systems," in IEEE Transactions on Microwave Theory and Techniques, pp. 2625-2629, 2000. 6. R. K. Kokkonda, et al., "A SiC based Two-Stage Pulsed Power Converter System for Laser Diode Driving Applications," 2022 IEEE Energy Conversion Congress and Exposition (ECCE), pp. 1-8; P. 7. Asbeck, et al., "ET Comes of Age: Envelope Tracking for Higher-Efficiency Power Amplifiers," in IEEE Microwave Magazine, pp. 16-25, 2016. KEYWORDS: -Ga2O3; radiation-hard; high temperature; vertical devices; envelop tracking; pulse power RF; converter.
