Band structure and ultraviolet optical transitions in ErN

Abstract

Erbium nitride (ErN) is a rare-earth metal mononitride continuing to receive interest due to its unique electronic, magnetic, and optical properties. ErN has shown promise in the development of new functional materials for optoelectronic and spintronic devices. Here, we report on the optical properties of ErN crystals, grown by sublimation and probed by photoluminescence (PL) spectroscopy at both room temperature and 180 K. Multiple transition lines were observed between 2 and 4.5 eV. Using the PL results together with reported calculations, a coherent picture for the band structure at the Γ-point for ErN crystals was derived. PL results revealed that ErN has a minimum direct energy gap of 2.41 eV and a total of two valence bands and two conduction bands at the Γ-point separated by about 0.15 eV and 0.34 eV, respectively. These transitions reveal optical properties of ErN in the UV region and its band structure at the Γ-point.

Vibrational Spectrum and Thermal Conductivity of Rare‐Earth Semiconducting Erbium Nitride Thin Films

“…Photoemission measurement on the ErN crystals though initially had suggested a direct bandgap of %1 eV, subsequent low-temperature PL measurement showed a minimum bandgap of %2.4 eV, which is consistent with the reports in the 1960s. [1,10] PL measurements also showed the presence of two valence bands and two conduction bands at the Γ-point that are separated by 0.15 and 0.34 eV, respectively, in ErN. [10] While the experimental research on thin-film ErN has been inadequate, first-principles modeling analysis initially suggested ErN be a zero-gap semiconductor with the top of the valence band situated at the Γ-point, and the bottom of the conduction band located at the X-point of the Brillouin zone, respectively.…”

“…[1,10] PL measurements also showed the presence of two valence bands and two conduction bands at the Γ-point that are separated by 0.15 and 0.34 eV, respectively, in ErN. [10] While the experimental research on thin-film ErN has been inadequate, first-principles modeling analysis initially suggested ErN be a zero-gap semiconductor with the top of the valence band situated at the Γ-point, and the bottom of the conduction band located at the X-point of the Brillouin zone, respectively. [2] However, as traditional density-functional theory (DFT) calculations underestimate the bandgap of semiconductors, such predictions are not surprising.…”

“…ErN is ferromagnetic below a Curie temperature of 6 K and exhibits a lattice constant of 4.85 Å. [8][9][10] ErN micron-sized particles have already been commercialized for Gifford-McMahon (GM) cryo-coolers that show a very high cooling power due to the large cryogenic temperature-specific heat of ErN. [11] Even though research on ErN has been gaining attention in the last few years, Er-doped semiconductors have been studied for over 20 years for various applications.…”

“…Photoemission measurement on the ErN crystals though initially had suggested a direct bandgap of ≈1 eV, subsequent low‐temperature PL measurement showed a minimum bandgap of ≈2.4 eV, which is consistent with the reports in the 1960s. [ 1,10 ] PL measurements also showed the presence of two valence bands and two conduction bands at the Γ‐point that are separated by 0.15 and 0.34 eV, respectively, in ErN. [ 10 ]…”

“…[ 1,10 ] PL measurements also showed the presence of two valence bands and two conduction bands at the Γ‐point that are separated by 0.15 and 0.34 eV, respectively, in ErN. [ 10 ]…”