Hole to Electron Crossover in a (Cd,Mn)Te Quantum Well through Surface Metallization

TL;DR

This study investigates how different surface metals affect the charge type in a CdTe quantum well, revealing that gold and nickel can switch the local doping from p-type to n-type due to their bonding properties.

Contribution

It demonstrates the influence of specific contact metals on the local charge properties of a CdTe quantum well, highlighting surface metallization as a method to control doping.

Findings

Gold and nickel flip the doping from p-type to n-type.

Most metals preserve the original p-type doping.

Surface metallization can enhance electron diffusion into the quantum well.

Abstract

In this work we look into how the contact material influences the local charge properties of a p-type CdTe-based quantum well. We study five metals deposited as 10 nm layers on the sample surface: Au, Ag, Cr, Ni and Ti. We use magneto-spectroscopy to discriminate their charge states through monitoring the Zeeman shifts at singlet-triplet transitions. Most tested metals retain the original p-type of the QW, while gold and nickel coverage flips the local doping to n-type. This is attributed to a robust bonding of these two metals to the semiconductor, efficiently passivating its surface and thus improving electron diffusion from the metal to the quantum well.