Work

Transferable Freestanding Varactor Based on a Membrane Stack for Microwave Application

Year: 2025

Type: article

Abstract: This work demonstrates the fabrication and characterization of a freestanding oxide varactor membrane designed for integration onto silicon substrates. An epitaxial varactor heterostructure composed of a 1% Mn-doped Ba$_{0.5}$Sr$_{0.5}$TiO$_{3}$dielectric layer and a SrMoO3conductive layer was grown using pulsed laser deposition on a water-soluble sacrificial layer Sr3Al2O6. After the lift-off process, the varactor heterostructure was successfully transferred onto a silicon substrate. Structural analysis confirms the high crystallinity and strain relaxation of the heterostructure after transfer. Electrical measurements reveal high tunability (n=1.7) at 120 V/$\mu$m, a quality factor exceeding 100 at 1 MHz, and a low leakage current density well below 5 A/m2. This approach overcomes the challenges of direct oxide growth of epitaxial varactor heterostructures on silicon, such as lattice mismatch and chemical incompatibility. These results validate the potential of freestanding varactor membranes for agile microwave and RF applications, offering a scalable route for high-performance, multifunctional devices with low energy consumption in next-generation telecommunications and wireless networks.

Source: IEEE Transactions on Materials for Electron Devices

DOI: 10.1109/tmat.2025.3580484

Authors: Yating Ruan, Philipp Komissinskiy, Alexey Arzumanov, Holger Maune, Lambert Alff

Institutions: Technische Universität Darmstadt, Otto-von-Guericke-Universität Magdeburg

Language: English

Topic: Advanced MEMS and NEMS Technologies

Subfield: Electrical and Electronic Engineering

Field: Engineering

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $2,645

Funder: Deutsche Forschungsgemeinschaft