Heterogeneous integration of superconducting thin films and epitaxial semiconductor heterostructures with Lithium Niobate

TL;DR

This paper demonstrates scalable integration of superconducting films and semiconductor quantum dots on lithium niobate, enhancing acoustic resonator quality and enabling quantum phononic and optoelectronic applications.

Contribution

It introduces a novel heterointegration process combining superconducting niobium nitride and III-V semiconductors on lithium niobate, with improved device performance and quantum coupling capabilities.

Findings

Surface acoustic wave resonators with superconducting electrodes achieve high quality factors (~17000).

Superconducting resonators operate efficiently above 7 K and +9 dBm RF power.

Quantum dots are coupled to phononic fields, enabling quantum control and transduction.

Abstract

We report on scalable heterointegration of superconducting electrodes and epitaxial semiconductor quantum dots on strong piezoelectric and optically nonlinear lithium niobate. The implemented processes combine the sputter-deposited thin film superconductor niobium nitride and III-V compound semiconductor membranes onto the host substrate. The superconducting thin film is employed as a zero-resistivity electrode material for a surface acoustic wave resonator with internal quality factors $Q \approx 17000$ representing a three-fold enhancement compared to identical devices with normal conducting electrodes. Superconducting operation of $\approx 400\,\mathrm{MHz}$ resonators is achieved to temperatures $T>7\,\mathrm{K}$ and electrical radio frequency powers $P_{\mathrm{rf}}>+9\,\mathrm{dBm}$. Heterogeneously integrated single quantum dots couple to the resonant phononic field of the surface acoustic wave resonator operated in the superconducting regime. Position and frequency selective coupling mediated by deformation potential coupling is validated using time-integrated and time-resolved optical spectroscopy. Furthermore, acoustoelectric charge state control is achieved in a modified device geometry harnessing large piezoelectric fields inside the resonator. The hybrid quantum dot - surface acoustic wave resonator can be scaled to higher operation frequencies and smaller mode volumes for quantum phase modulation and transduction between photons and phonons via the quantum dot. Finally, the employed materials allow for the realization of other types of optoelectronic devices, including superconducting single photon detectors and integrated photonic and phononic circuits.