【International Papers】Polarized photoluminescence from Sn, Fe, and unintentionally doped β-Ga₂O

      Researchers from the University of Utah have published a dissertation titled " Polarized photoluminescence from Sn, Fe, and unintentionally doped β-Ga₂O₃ " in Journal of Vacuum Science & Technology A.

ABSTRACT

      In this work, we demonstrate that β-Ga₂O₃ shows orientation-dependent polarized photoluminescence (PL) emission and give a comprehensive insight into gallium oxide's PL spectral properties. We characterized the polarization and spectral dependencies of both the incident and emitted light for (−201) unintentionally doped (UID) as well as (−201) and (010) Sn-doped and Fe-doped crystals. We observed for UID and Sn-doped samples that the electron to self-trapped hole and native defect-related emission bands are linearly polarized with polarized emission intensities ordered as E || c (and c*) > E || a (and a*) > E || b. Furthermore, the spectral shape of emission does not change between the UID and Sn-doped samples; instead, the Sn-doping quenches the total PL spectral intensity. For Fe-doped samples, polarized red emission caused by unintentional Cr³⁺ doping generates emission intensities ordered E || b > E || c (and c*) > E || a (and a*). It is also observed that in some circumstances, for some doped crystals, the PL spectra can show variations not only in intensity but also in spectral shape along different polarization directions. As an example, the PL emission band for emission along c is blueshifted relative to that along a in Sn-doped β-Ga₂O₃.

FIG. 1. Crystal structure of β-Ga₂O₃ showing the (−201) plane and the [102] direction along (a) a orientation, (b) b orientation, and (c) c orientation.

FIG. 2. PL spectra of (−201) UID β-Ga₂O₃. (a) PL spectra at different polarization excitations while emission is not polarized. Excitation is at 240 nm (5.16 eV). The inset is the same plot normalized. (b) PLE of the integrated PL spectra for E_in|| b – E_in|| [102] and then divided by the sum of the two. The points circled indicate the excitation wavelengths used for PL spectral measurements. (c) PL spectra at different polarization emissions excited at 240 nm (5.16 eV) with excitation E_in || b. The inset is the same plot normalized. (d) PL spectra at different polarization emissions excited at 267 nm (4.64 eV) with excitation E_in || [102]. Missing data in the graph are from the 2nd harmonic of the excitation laser. The inset is the same plot normalized.

Paper Link：https://doi.org/10.1116/6.0003216