Selective incorporation of antimony into gallium nitride

TL;DR

This study uses first-principles calculations to reveal that antimony can incorporate into gallium nitride as both an anion and cation, affecting its optical properties and enabling tunable light emission.

Contribution

It demonstrates the dual incorporation mechanisms of Sb into GaN and how growth conditions influence its electronic and optical properties, providing new insights for material engineering.

Findings

Sb can be incorporated as both anion and cation in GaN.

Coexistence of multiple Sb states explains experimental spectra.

Selective Sb incorporation modifies GaN's electronic properties.

Abstract

Dilute concentrations of antimony (Sb) incorporation into GaN induce strong band-gap bowing and tunable room-temperature photoluminescence from the UV to the green spectral regions. However, the atomistic details of the incorporation of Sb into the GaN host remain unclear. In this work, we use first-principles calculations to understand the thermodynamics of Sb substitution into GaN, and its effect on the optical and Raman spectra. Although it is empirically considered that Sb is preferentially incorporated as an anion ($\mathrm{Sb^{3-}}$) into the N sublattice, we demonstrate that Sb can also be incorporated as a cation ($\mathrm{Sb^{3+}}$, $\mathrm{Sb^{5+}}$) into the metal sublattice. Our thermodynamic analysis demonstrates that $\mathrm{Sb_N^0}$, $\mathrm{Sb_{Ga}^{2+}}$, and $\mathrm{Sb_{Ga}^0}$ can co-exist under Ga-rich conditions in n-type samples. We further confirm the dual incorporation of Sb by calculating the vibrational frequencies of different anionic and cation substitutions to explain the origins of experimentally observed additional Raman peaks of Sb-doped GaN. Moreover, the calculated band structures of different Sb substitutions into GaN explain the experimental photoluminescence and optical absorption spectra. Overall, our analysis suggests that the coexistence of $\mathrm{Sb^{3-}}$, $\mathrm{Sb^{3+}}$, and $\mathrm{Sb^{5+}}$ substitutions into GaN explains the totality of experimental measurements. Our results demonstrate that the selective incorporation of Sb into GaN (and potentially other group-V elements such as As, P, or Bi) by tuning the growth conditions can drastically modify the electronic properties, for applications in visible light emitters and photocatalysis.