Shift of Fermi level by substitutional impurity-atom doping in diamond and cubic- and hexagonal-boron nitrides

TL;DR

This study investigates how substitutional impurity doping shifts the Fermi level in diamond and boron nitrides, identifying critical dopant concentrations that induce semiconductor-to-metal transitions and potential superconductivity.

Contribution

It provides detailed computational analysis of Fermi level shifts due to specific dopants in diamond and boron nitrides using the KKR scheme, highlighting critical doping levels for electronic transitions.

Findings

Fermi level shifts at specific dopant concentrations

Critical dopant levels for semiconductor-metal transition

Potential for superconductivity in B-doped diamond

Abstract

The density of states and the band diagrams were computed for diamond, cubic boron nitrde (cBN), and hexagonal boron nitride (hBN) using a Korringa-Kohn-Rostoker (KKR) scheme to investigate the shift of the Fermi level by impurity-atom doping below 10 at.%. The dopant atoms were B and N for diamond, Be, Si, and C for cBN, and Be and C for hBN. It was found that the Fermi level was located at the valence band maximum or the conduction band minimum in the following seven cases: (i) the B concentration was 0.3 at.% in B-doped diamond, (ii) the N concentration was 0.4 at.% in N-doped diamond, (iii) the concentration of Be substituting B was 0.9 at.% in cBN, (iv) the concentration of Si substituting B was 0.3 at.% in cBN, (v) the concentration of C substituting B was 0.3 at.% in cBN, (vi) the concentration of C substituting N was 0.9 at.% in cBN, and (vii) the concentration of Be substituting B was ~2 at.% in hBN. Each of these values indicates the critical dopant concentration for semiconductor-to-metal transition. In B-doped diamond, it serves a measure for the occurrence of superconductivity at low temperature.