Cr resonant impurity for studies of band inversion and band offsets in IV-VI semiconductors

TL;DR

This study investigates Cr dopants in IV-VI semiconductors, revealing Fermi level pinning, band offsets, and multiple charge states of Cr, which are crucial for electronic device design.

Contribution

It provides a detailed analysis of Cr impurity states and their effects on band structure and offsets in IV-VI semiconductors using combined experimental and theoretical methods.

Findings

Fermi energy pinning to Cr resonant level in PbSnTe and PbSe.

Determination of valence and conduction band offsets at heterointerfaces.

Identification of Cr in three charge states, including interstitial incorporation.

Abstract

Understanding the electronic structure of transition-metal dopants in IV-VI semiconductors is critical for tuning their band structure. We analyze properties of Cr dopant in $Pb_{1-x}Sn_xTe$ and PbSe by magnetic and transport measurements, which are interpreted based on density functional calculations. We demonstrate that the pinning of the Fermi energy to the chromium resonant level occurs for both n-type and p-type $Pb_{1-x}Sn_xTe$ in the whole composition range. This enables us to determine the valence band and conduction band offsets at the PbTe/SnTe/PbSe heterointerfaces, which is important for designing high-prformance 2D transistors. Furthermore, the magnetic measurements reveal the presence of Cr ions in three charge states, $Cr^{3+}$, $Cr^{2+}$, and $Cr^{1+}$. The last one corresponds to the Cr dopants incorporated at the interstitial, and not the substitutional, sites. The measured concentrations of the interstitial and substitutional Cr are comparable.