# A Substrate-Reclamation Technology for GaN-Based Lighting-Emitting Diodes Wafer
## 3 Results and Discussion  
Figure 2 shows top-view and cross-section scanning electron microscope (SEM) images of GaN-epi/PSSs both exposed and not exposed to gas-flow rates of 10 sccm for 30 min and at various temperatures (800-1200 \({}^{\circ}\)C). Figure 2a shows the surface morphology and cross-section of the GaN-epi/PSSs (i.e., original samples). In addition, the top-view SEM image of the original pristine sapphire substrate is also shown in the inset of Figure 2a. Preparing the GaN-epi/PSSs at 800 \({}^{\circ}\)C changed the surface morphology of the GaN-epi film, as shown in Figure 2b. Upon increasing the process temperature to 1000 \({}^{\circ}\)C, sheet-shape decomposition began in the GaN epilayers and the substrate cone patterns started to exposed, as shown in Figure 2c. Further increasing the temperature \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample: GaN-epi/PSSs Experimental Conditions** & **Temperature/\({}^{\circ}\)C** & **Gas-Flow Rates/sccm** & **Times/min** \\ \hline \hline \multicolumn{4}{c}{I. Processes under different temperatures} \\ \hline Sample A & 800 & & \\ Sample B & 1000 & 10 & 30 \\ Sample C & 1200 & & \\ \hline \hline \multicolumn{4}{c}{II. Processes under different times} \\ \hline Sample D & & & 30 \\ Sample E & 1200 & 25 & 60 \\ Sample F & & & 90 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Substrate-reclaim conditions of GaN-epi/patterned sapphire substrate (PSS). Figure 1: Schematic diagram showing substrate-reclaim setup for GaN-epi/patterned sapphire substrate (PSS) by furnace process in H\({}_{2}\) gas. to 1200 \({}^{\circ}\)C resulted in cone patterns appearing over the entire sample surface. Figure 2d,e show the top view and cross-section and an enlarged schematic of the PSS after being exposed to a gas-flow rate of 10 sccm for 30 min at 1200 \({}^{\circ}\)C. The PSS cone diameter, spacing, and height were 3.33, 2.71, and 1.04 \(\upmu\)m, respectively. By comparing them with the original cone pattern, these results indicate that the GaN-epi film still did not completely decompose under these process conditions. In addition, the GaN-epi decomposition reaction correlated positively with the process temperature, which is consistent with the results of [PERSON] et al. [11]. Figure 3 shows the X-ray diffraction (XRD) spectra of the GaN-epi/PSS prepared and not prepared according to substrate-reclamation process I. The diffraction pattern from untreated GaN-epi/PSS has a sharp GaN (002) peak near 34.6\({}^{\circ}\), several satellite peaks from the InGaN/GaN active layers, and a sapphire (001) peak near 2\(\theta\) = 41.6\({}^{\circ}\), as shown in Figure 3a. The grazing-angle XRD spectra of samples A, B, and C appear in Figure 3b-d, respectively. The diffraction peaks from the GaN (103) phase near 2\(\theta\) = 63.6\({}^{\circ}\) gradually began to weaken with increasing the temperature from 800-1200 \({}^{\circ}\)C. Moreover, when the operation temperature exceeded 1000 \({}^{\circ}\)C, a GaO\({}_{2}\)H (110) peak near 2\(\theta\) = 21.47\({}^{\circ}\) appeared in the diffraction pattern. These results indicate that the GaN-epi film on the PSS begins to transform and to produce a GaO\({}_{2}\)H derivative. Note that the GaN-epi film still exists under the conditions of process I. Figure 4 shows the grazing-angle XRD spectra of the GaN-epi/PSS prepared using substrate-reclamation process II. The diffraction pattern reveals a GaO\({}_{2}\)H (110) peak at 2\(\theta\)\(\cong\) 21.47\({}^{\circ}\)  
Figure 2: Top-view and cross-section scanning electron microscope (SEM) micrographs of GaN-epi/PSS prepared and not prepared according to substrate-reclamation process I. The enlarged schematic diagram of the PSS in panel (**e**) depicts the cone pattern size of sample C.  
and a sapphire (012) peak at \(2\theta\cong 25.65^{\circ}\). As the process time increased from 30 min to above 60 min, the diffraction peaks of the sapphire (113) phase appeared near 43.47\({}^{\circ}\).