Impedance-engineered quantum layer for broadband reflection suppression in electron transport

Suppressing interfacial reflection is a central challenge in coherent electron transport because it limits transmission efficiency across semiconductor heterostructures. While quarter-wave antireflection layers—the electronic analog to optical coatings—are common, they are intrinsically limited by narrow operating bandwidths and angular sensitivity. Here, we establish a quantum impedance-engineered framework for broadband reflection suppression by formulating a universal impedance matching condition for matter waves in media with spatially varying effective mass m(z) and potential V(z). Unlike quarter-wave antireflection layers that are restricted to a single design point, the broadband nature of the universal impedance matching framework significantly enhances coherent electron transport. This is particularly critical for practical applications where the total performance of electron transport is determined by transmission averaged over a broad range of incident energies and angles. To implement the universal impedance matching condition in practical systems, we introduce an effective universal impedance-matching multilayer composed of nondispersive sublayers that approximate the ideal, dispersive target impedance. Numerical calculations demonstrate that the effective universal impedance-matching multilayer structure suppresses reflectance over a significantly wider energy-angle phase space than standard quarter-wave antireflection designs of equivalent thickness. Furthermore, we present an effective-impedance retrieval method to reconstruct the multilayer's response from scattering coefficients, confirming that the structure produces the ideal target matching impedance. This broadband enhancement translates directly to higher ballistic conductance and lower ballistic resistance within the Landauer–Büttiker transport framework. Our results establish impedance matching as a general design principle for electron-wave heterostructures, offering a practical strategy for developing high-transparency, low-resistance nanoelectronic devices.