GaAsSb/GaAsSbN Heterostructure Nanowires-based Short Wavelength Infrared Photodetectors

Approved for Public Release The focus of the proposed work in the short wavelength infrared (SWIR) region photodetectors (PDs) is dr,iven by next-generation requirements for high sensitive PDs that can be heterogeneously integrated with silicon technology. Addition,al demands on these PDs are small size, weight, and low power (SWaP) capability to keep pace with the improvements in focal planar t,echnology and integrated-read-out circuitry for high-resolution imaging under all weather conditions for the Navy.Bandgap engineerin,g of heterostructures comprising GaAsSb and dilute nitride GaAsSb material systems in nanowire (NW) geometry offers a potential solu,tion to address such challenges. The dilute nitride material system shows a significant bandgap reduction by incorporating N in the, 1-2% range in the GaAsSb lattice, concurrently reducing the lattice parameter and enabling bandgap tailoring over a wide range. The, strain engineering of the heterostructure of GaAsSb and GaAsSbN, hitherto referred to as HT, will enable band tuning in the SWIR re,gion. A device design where a large bandgap such as AlAsSb material is sandwiched between the two n-doped HT structures would allow, dark current reduction by suppressing the generation and surface leakage current components. Implementation of this design in the N,W configuration enables leveraging the outstanding optoelectronic properties of one-dimensional architecture, namely superior optica,l trapping features of vertically aligned NWs and integration on a Si platform. The small cross-section of the NWs also further supp,resses the phonon component of the current contribution, improving the device sensitivity, and enabling higher operational device te,mperatures. The proposed effort is based on our group?s past synergistic activities on the n-doped GaAsSbN NWs based on Schottky bar,rier (SB) PDs on Si and achieving 1.7-micron room temperature photoluminescence emission in the HT-strain engineered NWs. A molecul,ar beam epitaxy system will synthesize these NWs in the SWIR region. A systematic and comprehensive study on HT-structured NWs passi,vated with GaAlAs shell, and corresponding SB device on (111) Si will be carried out using various materials and device characteriza,tions. Using this optimized HT, nBn-configured NWs with the AlAsSb barrier layer and GaAlAs as the outermost passivating shell will, be explored in the core-shell geometry. Emphasis will be on the temperature dependence of the dark current, low-frequency noise, an,d lifetime measurements of the carriers and correlating them to achieve PD of high detectivity at 1.7 micron. These NWs will be impl,emented in a patterned array, and the array pitch and diameter will be tailored to achieve detectivity exceeding 1013 Jones at 1.7 m,icron. This experimental work will be guided by semi-empirical modeling using a combination of software packages. Another component, of this project is to fabricate flexible devices by embedding the NWs in a suitable polymer, then peeling off the NWs and placing t,hem on a flexible substrate. Multispectral PDs will be fabricated by stacking these, one on top of the other. Successful completion, of this work will b,vity and flexible devices of great relevance to the Navy. This program?s other important goal is to establish a pipeline that nurtu,res and creates the next generation of minority engineers by exposing them to Navy-relevant projects with well-defined research goal,s, providing them with the skills necessary to apply scientific knowledge to a novel, paradigm-shifting low-dimensional-based detect,or technologies.