Exploring negative differential resistance effects in monolithic Al-Ge-Al heterostructures

Abstract

Germanium (Ge) is of particular interest for the investigation of quantum effects due to its pronounced spin-orbit coupling and quantum confinement phenomena [1]. In addition toongoing miniaturization, Ge presents notable performance advantages for integrated ICs owing to its elevated carrier mobility and compatibility with Complementary Metal-Oxide-Semiconductor (CMOS) technology [1]. Over recent years, Vapour Liquid Solid (VLS) grown nanowires (NWs) have served as the foundation for Al-Ge heterostructures [2], facilitating significant advancements in quantum ballistic transport, photonic, and plasmonic investigations[2]. This progress holds the potential for the development of a diverse array of cutting-edge devices [2]. Despite its potential, the large-scale integration of VLS-grown Ge-NWs poses significant challenges [2].Negative Differential Resistance (NDR) phenomenon is a non-linear electrical behavior observed in a variety of materials and devices [3]. This study presents an in-depth investigation into the NDR behavior exhibited by Al-Ge-Al nanostructures. The results are observed inmultiple NDR features in NWs. In the experimental section of this thesis, various analyses were conducted to investigate how the observed phenomena in Al-Ge-Al nanostructures depend ontheir physical dimensions [3]. This involved systematically varying parameters such as the length, width, and thickness of the NWs to understand their influence on properties like NDR behavior and conductivity. By meticulously controlling these parameters, i was able to uncover trends and correlations that shed light on the underlying physics governing the behavior of these nanostructures [3].In essence, the NDR behavior observed in Al-Ge-Al NWs stems from intricate interactions among electronic states within the constituent materials. The investigation yields profound insights into the fundamental physics governing NDR phenomena in NW systems, offering promising avenues for future nano-electronic applications [3].Crystallographic analyses uncover the exceptional purity and crystallinity of Al-Geheterostructures, featuring nearly atomically sharp interfaces [4]. Our exploration of structures with diverse cross-sections demonstrates the versatility of the thermal Al-Ge exchange process,which exhibits no constraints based on specific orientations or geometric boundaries [4]. The markedly improved contact characteristics of the abrupt metal-semiconductor junction contribute to a remarkable enhancement in the conductivity of an nealed heterostructures [5].Integration of these advanced heterostructures into field-effect transistor (FET) architecturesenables precise modulation of drain current across multiple orders of magnitude [5].