Figure 2.

Part of the PL spectrum from undoped GaN. Sample H3. T = 18 K, P _exc = 5 × 10⁻⁵ W/cm². The long-dashed and short-dashed lines show shapes of the YL1 and RL1 bands, respectively, obtained using Eq. (1) with the following parameters: $I_{\max }^{PL}=0.98\times {10}^8$, S _e = 7.4, E ₀ ^* = 2.67 eV, $\hslash {\omega }_{\max }=2.21$ eV (for the YL1 band) and $I_{\max }^{PL}=1.88\times {10}^8$, S _e = 10, E ₀ ^* = 2.33 eV, $\hslash {\omega }_{\max }=1.76$ eV (for the RL1 band). The × symbols show the sum of two simulated bands. ZPL is the zero-phonon line of the YL1 band at 2.575 eV.