Dilute Nitride GaAsSbN Nanowires Based High-Speed Near-Infrared Photodetectors

The focus of the proposed work is to meet the demands of next-generation high speed, high-performance, heterogeneous integration with silicon technology and low-cost photodetectors (PDs) in the near-infrared (NIR) wavelength region for a variety of Army applications, namely, high-resolution imaging/surveillance, enhanced situational awareness, night vision, and ranging. PDs of dilute nitride mixed As-Sb material system in the nanowire (NW) geometry offer a potential solution to address such challenges. This material system shows huge bandgap reduction by incorporating N in the 1- 2% range in the GaAsSb lattice, enabling bandgap tuning over the entire NIR range. It allows independent control of valence and conduction band offsets by varying Sb and N composition, respectively. Implementing this material system in the NW configuration allows leveraging the outstanding optoelectronic properties of one-dimensional architecture, namely superior optical trapping features of vertically aligned NWs, core-shell (CS) architecture exclusive to one-dimensional configuration well-suited for high-speed devices without sacrificing PD responsivity and detectivity, and integration on Si platform due to large tolerance for lattice mismatch. The proposed effort is based on our groupÕs past successful and synergistic activities on the GaAsSbN NW ensemble-based PD on Si in the NIR region and GaAsSb NW-based PD on graphene. A molecular beam epitaxy system will be used to synthesize these NWs in the NIR region (1-1.6 µm). A systematic and comprehensive study of GaAsSbN NWs and corresponding Schottky barrier device on (111) Si with various materials and device characterizations will be performed to obtain a fundamental understanding of the nature of the N-induced defects and their annihilation in order to tailor the carrier lifetime to enhance the device speed. The impacts of Si and graphene substrates on the material quality and device speed will be investigated. During the final phase, the design optimization of p-i-n junction configured GaAsSbN/GaAsSb NWs and patterned NW arrays in the CS geometry will be studied, with an emphasis on 3-dB bandwidth and detectivity. This experimental work will be guided by semi-empirical modeling using a combination of software packages. The other important component of this program is to nurture the next generation of minority engineers in cutting-edge technology by exposing them to Army-relevant projects of well-defined research goals and providing them with the skills necessary to apply scientific knowledge to a novel, paradigm-shifting low dimensional based detector technologies. Successful completion of this work will broaden the choice of material base and provide a novel pathway to achieve high speed and high-performance devices of great relevance to Army applications. Also, the bandgap engineering study can be extended in the future to other dilute nitride material systems, encompassing mid-wavelength and long-wavelength regions of great interest to the Army.