3.9 Electronic Materials

3.9.1 Warfighter Needs

Warfighters are increasingly exploiting electronic systems to achieve not only force multiplication but also the performance edge that promotes battlefield dominance. Much of this edge results from advances in devices developed for military-specific needs, advances that often exploit new capabilities provided by Electronic Materials technologies. Both the performance and cost of radar, communications, information warfare, and other electronic systems depend directly on the reproducibility, quality, and cost of electronic materials synthesis and processing, as well as the ability to tailor materials characteristics. Advances in the Electronic Materials subarea transition into the RF Components, Electro-Optics, and Microelectronics subareas which, in turn, transition into the Sensors subareas and the ATR and Integrated Platform Electronics subareas, as well as many outside the Sensor, Electronics, and Battlespace Environment DTAP. This subarea therefore strongly supports almost all of the Joint Warfighter Science and Technology (see Figure 1.3). For example, advances in III-V semiconductor substrate and films have led to revolutionary new devices that will make more compact radars and higher frequency/data rate communication systems possible in the midterm (3-5 years). In the midterm and long term, materials for infrared focal plane arrays (IRFPAs) will make modules possible that will be capable of broader-band detection and multiple color response for enhanced surveillance and room temperature operation for high-sensitivity mobile night vision equipment; wide-bandgap semiconductors will make electronics available that operates at 300-500C (e.g., near engine components), as well as compact ultraviolet lasers for full-color displays, high density data storage for C4I, and covert communications. Because advances in electronic materials technologies can frequently be integrated into civilian use, even though the civilian utilization alone could not support the necessary development, DoD programs will benefit the civilian technology base, whose enhanced capabilities can then be used to satisfy military applications.

3.9.2 Electronic Materials Overview

The Electronic Materials subarea is directed toward the creation of new materials and the improvement of existing materials intended for device applications. It is not aimed at tailoring capabilities of specific devices (e.g., by improving a particular device parameter). Device/component performance, reliability, and reduced cost are the benchmarks of success. This subarea encompasses chemical synthesis; bulk and thin film/nanostructure materials fabrication; development of materials fabrication processes; and electrical, optical, structural, morphological, and chemical characterization. Classes of interest include semiconductor, superconductor, ferro/ferrimagnetic, ferroelectric, and nonlinear optical (NLO) materials.

3.9.2.1 Goals and Timeframes. The Electronic Materials subarea develops materials, fabrication processes, and device structures that are not supported commercially; are necessary for developing RF, microelectronics, and electro-optical (EO) devices and components; and combine affordability and reliability with high performance for use in DoD systems. Some specific embodiments of these goals are:

3.9.2.2. Major Technical Challenges. Threads that link most Electronic Materials efforts are the need to reduce the concentration of deleterious defects; to control material composition (including judicious introduction of intentional impurities), structure, and morphology in order to tailor properties; and to develop fabrication and characterization methods that result in high quality materials at affordable prices. Additional challenges depend upon specific materials and the maturity of the technology. The near-term challenge for high temperature semiconductors and HTS materials, both of which are at early stages of development, is to produce material having properties suitable for demonstration devices and small-scale components. Substrates that match the lattice constants and thermal expansion coefficients of III-N films are especially needed. For the more nearly mature GaAs- and InP-based materials, challenges include fabrication of larger-diameter substrates having lower defect densities, higher uniformity, and lower cost; further controlling and exploiting the relationships among growth environments and resulting propertiesparticularly controlling heterostructure interfaces such as InGaAs/InP and minimizing the strain induced by lattice mismatches between constituents of the heterojunctions. Key technical challenges for IR detector materials are the achievement of greater uniformity, more precise process control, and, for heterostructure detectors, control of interfaces and strain.

3.9.2.3 Related Federal and Private Sector Efforts. In the US, AT&T, H-P, Texas Instruments, Raytheon, Lincoln Lab, Hughes, and several universities have important III-V epi programs. NIST works with AF-RL/ERX and AF-WL/ELD to characterize wafers manufactured by contractors in the Title III GaAs substrate program. M/A-COM, Litton Airtron, and AXT market GaAs substrates; Crystacomm and AXT produce InP substrates (however, none conducts significant internally funded R&D). H-P, APA Optics, ATMI, and some universities conduct important III-N work. Cree, Westinghouse, and NC State University fabricate SiC. NASA, NIST, LANL, Sandia, ANL, Lincoln Lab, AT&T, IBM, Westinghouse, Conductus, Superconductor Technologies, Dupont, and several universities have important HTS programs.

3.9.3 S&T Investment Strategy

3.9.3.1 Technology Demonstrations. Electronic Materials is primarily an enabling technology. Upon optimization of materials or processing technology, the technology is ordinarily transitioned to device development projects and to industry for scale-up or commercialization. Electronic materials are "demonstrated" by successful transitions into the device/component community.

3.9.3.2 Technology Development. By targeting high-leverage technologies, notably materials technologies that have diverse electronic and electro-optic applications, this subarea anticipates the needs of the DoD electron device and component communities. The work includes: [a] development of nonlinear optical (NLO) materials for mid-IR optical amplifiers and oscillators (e.g., for frequency-agile lasers for electronic countermeasures) and materials for optical computing/storage, target recognition, and optical interconnects; [b] patterning and processing methods/materials/equipment to make possible still higher packing densities for electronics, reducing weight and increasing functionality; [c] development and technology transfer of promising process technologies that will lower production costs and enhance device/component performance and quality; and [d] HTS materials and structures whose near-zero RF electrical resistance can be exploited to create extraordinarily narrow-band filters and compact high-frequency, high-bandwidth antennas for jam-resistant, high-data-rate communications components. Additional efforts, summarized in the following subparagraphs, support DTOs.

3.9.3.2.1 Compact High Power RF Transmitters. DTO SE.19.01.NF. This DTO is supported by two areas of Electronic Materials R&D: Wide Bandgap Semiconductors, and Intermediate Bandgap III-V semiconductors. Wide bandgap semiconductor efforts focus on growing, cubic SiC substrates and on growing high quality (Al,Ga,In)N materials for high power RF and high temperature electronics. The III-N efforts include growth of lattice- and thermally-matched substrates (e.g., ZnO and LiAlO3, plus high-risk-high-payoff efforts to grow GaN as a substrate). Intermediate bandgap semiconductor efforts include development of advanced InP substrates; III-V films, heterostructures, and nanostructures grown on GaAs and InP substrates by OMCVD and MBE; and SiGe heterostructures for RF heterojunction bipolar transistors (HBTs). GaAs-based materials development is being pursued because GaAs still dominates microwave electronics. InP-based materials (plus antimonides) are being developed for possible displacement of GaAs in high power and low noise microwave amplifiers.

3.9.3.2.2 Advanced Infrared Focal Plane Array. DTO SE.22.01.ANFE. This effort emphasizes infrared detector materials for applications that include IRFPAs for surveillance and night/adverse weather operations. Films and structures based on HqCdTe monolithic films with on-chip processing, on InAs/GaSb superlattices (capable of detecting wavelengths >12 m) and on SiGe (for Schottky barrier devices) are being developed in pursuit of these goals.

3.9.3.2.3 Optical Control of Radar, Comm., and EW Systems. DTO SE.24.01.NFE; and Low Power Consumption Electronics DTO SE.21.01.FE. Intermediate bandgap III-V semiconductor efforts, described in para. 3.9.3.2.1, support these DTOs. Support for DTO SE.24.01.NFE derives from the fact that GaAs and InP are premier materials for high-speed light generation and detection, as well as for high-speed electronics. InP-based materials are the mainstay of optoelectronics for telecommunications, and thus are being developed for optically implemented control functions (e.g., of radar antenna remoting and true time delay control of phased array antennas) as well as for communications applications.

3.9.3.3 Basic Research. Electronic Materials technology opportunities are closely coupled to basic research. The latter creates the knowledge base undergirding the exploratory development efforts. This arose because Basic research provides the insight into material processes and properties which are exploited in the technology program. Most 6.2 efforts described above are organized so that 6.2 efforts have direct 6.1 counterparts and so they are synergistically intertwined.