## 4 Discussion  
In our PL measurements, the excitation source employs photons with energy greater than the bandgap of CdTe. These energetic photons are absorbed by the sample, promoting electrons from the valence band to the conduction band, thereby generating electron-hole pairs. Subsequently, these excited charge carriers relax to their ground state through various mechanisms. Radiative recombination processes, where electrons and holes recombine to emit photons, are the primary mechanisms responsible for the emission of light in PL spectroscopy. Our results indicate that the PL peak position is unaffected by changes in surface roughness. The consistency of the PL peak position suggests that the energy level associated with the fundamental radiative transition in the material, such as the bandgap, remains unchanged regardless of surface roughness. Furthermore, the decrease in PL spectrum intensity can be attributed to increased light scattering caused by greater surface roughness. This leads to lower photoluminescence emission efficiency. Surface irregularities contribute to additional light scattering and absorption, reducing PL intensity. On the other hand, the PL-emitted photon energy directly correlates with the energy difference between the involved electronic states, providing insights into the material's bandgap and defect-related energy levels. For CdTe, these energy levels are primarily attributed to native point defects, extended defects, and impurities or even the interactions between them [30]. Such defects act as recombination and trapping centers, often referred to as surface states, which influence carrier dynamics and recombination pathways. The interplay between these factors results in broadened and asymmetric PL spectra. Figure 4 shows the normalized PL spectra for regions with RMS roughness values of (a) 307 nm, (b) 467 nm, and (c) 602 nm. Blue lines represent experimental data. For clarity, spectra have been vertically offset. The experimental PL peaks shown in Figure 4 exhibit broad, asymmetric spectral profiles, suggesting the superposition of multiple emission processes. Here, deconvolution techniques can be employed to separate the composite  
Figure 3: Experimental resonant Raman scattering (RRS) spectra of CdTe for different RMS surface roughness values. The inset shows the correlation between the intensity of the 2 LO phonon mode and the RMS value of roughness. peak into its individual components, providing insights into the physical mechanisms contributing to the overall emission. To deconvolute the PL emission peak, we fitted each spectrum with three Gaussian functions corresponding to the deep, intermediate (also known as donor-acceptor pair or DAP), and excitonic spectral regions. We adopted this approach because the PL spectra of CdTe typically exhibit feature emissions in these three main spectral sections [31]. The deconvolution of the PL spectra into constituent Gaussian components reveals a primary peak centered on 1.5 eV, composed of three uniformly broadened Gaussian lines located at the position indicated by vertical arrows in Figure 4. The deconvolution results, represented by red lines, exhibit excellent agreement with the experimental data. The dominant spectral component corresponds to the deep region, typically associated with defects. As our sample is undoped, intermediate and excitonic region intensities are negligible and their fitting parameters remain relatively constant with varying surface roughness. Consequently, these contributions were disregarded. Figure 4 demonstrates a correlation between the FWHM of the deep region and RMS surface roughness, suggesting that surface roughness promotes the formation of surface states, thereby influencing the material's electronic structure. The correlation between surface roughness and FWHM of the PL peak suggests that smoother areas have fewer surface states and reduced nonradiative recombination in the deep region.