Figure 3
From: Incident wavelength and polarization dependence of spectral shifts in β-Ga2O3 UV photoluminescence
Theoretical analysis of the valence band states as an explanation for the observed UV emission wavelength shift under 266 nm excitation. (a) Computed β-Ga2O3 valence band structure along the k-path: Z = (0.0 0.0 0.5) − Γ = (0.0 0.0 0.0) − F = (0.0 0.5 0.0), where the points are colored terms of OI, OII and OIII contributions with blue, red, and green, respectively. (b) Projected density of states (PDOS) showing the O p-orbital contributions to the valence band for the three distinct crystallographic O sites. The calculated data is broadened with Gaussian and Lorentzians with a full-width half maximum of 0.10 eV. (c) Analysis of the dipole transition matrix elements from valence bands to the lowest-lying conduction band for each crystallographic direction, showing the relative contributions of each O site as a heatmap. All of the plots suggest that OII sites contribute the most to absorption processes involving the highest-lying valence bands. (d) Illustration of potential emission paths leading to the observed PL peaks based on the calculate polaron single-particle states. (e) Explanation of the observed UV PL wavelength shift on-basis of the observed peak being the ensemble of two distinct Gaussians corresponding to two distinct STH levels associated with the OI and OII sites.
