Study of PIN Junctions in GaAsSb Nanowires on Si for the Next Generation Infrared Photodetectors

The following proposal aims to carry out a comprehensive investigation of p-i-n (PIN) structured GaAsSb nanowires (NWs) of different architectures for near infrared-based photodetector (PD) applications. The one-dimensional configuration of NWs, typically 50 nm to 200 nm in diameter, offers unique electronic properties, and provides greater flexibility in material design and versatility in architecture. However, the large surface to volume ratio forms surface states that can have a deleterious effect on the material quality and device performance. Postgrowth annealing is one simple technique to quell these effects related to surface states. Accordingly, the focus of the study is to exploit the unique characteristics of NWs in the PIN-configured heterostructure and gain an understanding of the annealing effects on the annihilation of surface states, surface ordering, defect states, compositional homogeneity and redistribution of the dopants in the nanowires. The effects will then be correlated to the collection efficiency of the charge carriers, dark current and sources of noise in the device and their device performance. The enabling growth technology that can exploit this system to its full potential is molecular beam epitaxial (MBE) technique. By using a variety of characterization techniques for both material quality and devices, the annealing effects and correlation of the device performance parameters will be performed across the three NW architectures (axial, core-shell, and tapered). The techniques that will be employed include the following: low temperature microphotoluminescence, Raman spectroscopy, X-ray diffraction, scanning electron microscopy, temperature dependence I-V and low frequency noise measurements. The knowledge gained will be fundamentally rich and may contribute to the development of advanced futuristic photodetector applications that are pertinent to AFOSR. The PI has an extensive history of engaging postdoctoral research associates, graduate students, as well as undergraduate students in operating state-of-the-art MBE research equipment, characterization tools, in device fabrication processing and simulation. The research component is well integrated with the educational component beginning at the undergraduate level, and the program will continue to assist in developing and improving educational materials. It will also help grow the number of underrepresented students already participating in the nanomaterials and devices program with the skill set sought in AFOSR. Lastly, it will help accelerate and enhance the focused effort on strengthening our expertise in compound semiconductor-based nano-materials and devices at North Carolina A&T State University.