2025/01/19 by LuckyDonald L Kynshi, Umang Soni, Kynshi, LuckyDonald L +7
Engineering · Physics and Astronomy · #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Mesoscale and Nanoscale Physics (cond-mat.mes-hall) #Photonic and Optical Devices #Semiconductor Quantum Structures and Devices #Semiconductor materials and interfaces
paper · pdf · doi:10.48550/arxiv.2501.11059
openalex publication_date 2025/01/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Shallow undoped Si/SiGe quantum wells are the leading platforms for hosting quantum processors based on spin-qubits. The ohmic contacts to the electron gas in these systems are accomplished by ion-implantation technique since the conventional Au/Sb alloyed contacts present a rough surface consisting of sharp islands and pits. These sharp protrusions cause electrical discharge across the gate-dielectric between the ohmic contacts and the accumulation-gates causing device break-down. A clear understanding of the surface morphology, elemental, compositional and electrical characterization of the alloyed region would enable one to engineer a smoother post alloyed surface. In this work, we find that the rough surface morphology is a cumulative effect of the Au/Si eutectic reaction and the threading dislocations inherent in the heterostructure. The structural, elemental, and chemical-state analysis show that the inverted pyramidal pits are resulting from the enhanced Au/Si eutectic reaction at the threading dislocations stemming from the heterostructure interface, while, the sharp protrusions causing accumulation gate-leakage are gold-rich precipitations. The protrusions are removed using an aqua regia treatment prior to the deposition of the gate-oxide and gate electrode. Exploiting a Hall bar device, we analyse the mobility and carrier concentration of the undoped Si/SiGe consisting of Au/Sb alloyed contacts down to 1.5 K. The measured mobility ~105 cm2/Vs and carrier concentration of ~1011/cm2are comparable to the reported values on similar high-mobility heterostructures confirming the efficacy of our modified Au/Sb alloy technique in accomplishing high-efficiency contacts to undoped Si/SiGe heterostructures.