9.2.26

Article: Hole to electron crossover in a (Cd,Mn)Te quantum well through surface metallization

We explore how the choice of metal contact can profoundly influence the local charge environment in a CdTe-based quantum well. By depositing ultrathin metallic layers on the sample surface and probing the system with magneto-optical spectroscopy, we demonstrate that surface metallization alone can modify not only the carrier density but even the type of carriers present in the quantum well. While most of the investigated metals preserve the intrinsic p-type character originating from surface states, gold and nickel stand out by inducing a complete conversion to n-type doping.

Using a contactless, all-optical method, we identify the carrier type through the magnetic-field evolution of charged excitons, specifically by tracking singlet–triplet transitions. This approach avoids the need for gated structures or conductive substrates and enables a direct, local probe of carrier gases in low-dimensional systems. Results show that a simple picture based on metal work functions is insufficient to explain the observed behavior. Instead, the decisive role is played by strong metal–semiconductor bonding, which effectively passivates surface states and facilitates electron diffusion from the metal into the quantum well.

These findings highlight surface metallization as a powerful and flexible tool for charge engineering in semiconductor nanostructures. Beyond fundamental insight into surface-induced doping mechanisms, our work opens new possibilities for tailoring carrier properties in quantum wells, with potential applications in spintronics and quantum optoelectronic devices.

Authors: A. Dydniański, M. Raczyński, A. Łopion, T. Kazimierczuk, J. Kasprzak, K.E. Połczyńska, W. Pacuski, P. Kossacki

Solid State Communications 409, 116324

Published 10 January 2026

https://doi.org/10.1016/j.ssc.2026.116324