# Investigation of Hydrogen Flux Influence on InGaP Layer and Device Uniformity
## 3 Results and Discussion
### Influence of Total H\({}_{2}\) Flux on the Uniformity of the InGaP Single Layer
Figure 1: The sheet resistance measurements, corresponding to varying total H\({}_{2}\) fluxes, are shown sequentially for the rates of 15,000 sccm, 17,000 sccm, 19,000 sccm, and 21,000 sccm from (**a**) to (**d**). Figure 2b illustrates how variations in total H\({}_{2}\) flux impact the sheet resistance of InGaP epitaxial wafers. The graph shows an initial increase in sheet resistance as H\({}_{2}\) flux rises, followed by a slight decrease after a certain point. This trend can be attributed to the suppression of side reactions with increasing H\({}_{2}\) flux, enhancing gas convection and diffusion within the growth chamber. These improved gas dynamics lead to more uniform reactant distribution on the substrate surface, minimizing concentration gradient-induced side reactions. Consequently, the pathway for unintentional dopants to be incorporated into the epitaxial layer is shortened, reducing unintended doping and, thus, increasing the sheet resistance of the layer. However, once the H\({}_{2}\) flux reaches a specific threshold, further reductions in unintentional doping cease to be significant, leading to a stabilization in the rise of sheet resistance. Additionally, the intrinsic N-type character of InGaP may play a role; increased H\({}_{2}\) flux leads to a lower V/III ratio on the substrate surface, thus diminishing available group III element sites. This effectively hampers the incorporation of N-type dopants, thereby elevating the sheet resistance of the epitaxial layer. Figure 2b elucidates not only the effect of total H\({}_{2}\) flux on the sheet resistance of epitaxial wafers but also its crucial impact on resistance uniformity. Sheet resistance uniformity, a vital metric for assessing epitaxial wafer performance stability, offers valuable insights for refining the growth process and boosting device quality. The data indicate that sheet resistance uniformity undergoes a nuanced evolution with increasing H\({}_{2}\) flux, initially improving and then worsening before finally stabilizing. An initial enhancement in uniformity with moderate increases in H\({}_{2}\) flux suggests better mixing and diffusion of source gases within the growth chamber, facilitating more consistent epitaxial growth. However, as H\({}_{2}\) flux continues to rise, uniformity begins to diminish, possibly due to growth instabilities triggered by excessive flux, such as source gas concentration fluctuations or growth rate alterations, adversely impacting layer uniformity. Remarkably, at a H\({}_{2}\) flux of 19,000 sccm, sheet resistance uniformity peaks at an optimum of 0.53%, indicating that an optimal H\({}_{2}\) flux can lead to uniform epitaxial layer growth, laying the groundwork for devices with reliable performance. Furthermore, the impact of the H\({}_{2}\) flux rate on  
Figure 2: (**a**) Influence of total H\({}_{2}\) flux on epitaxial growth rate. (**b**) Impact of total H\({}_{2}\) flux on sheet resistance and its uniformity. uniformity exhibits distinct behaviors across different flux ranges. Below 19,000 sccm, sheet resistance uniformity varies more dramatically with flux changes, highlighting the flux's pronounced effect on the growth process within this spectrum. Beyond 19,000 sccm, however, uniformity variation with flux diminishes and shows signs of improvement with further increases, suggesting that a higher flux stabilizes gas flow and mixing within the chamber, thereby minimizing growth inhomogeneities. Our systematic investigation has unequivocally demonstrated the critical impact of total H\({}_{2}\) flux on the uniformity of InGaP single-layer epitaxial wafers, underscoring it as a pivotal parameter in the epitaxial growth process. The experiments suggest that optimal H\({}_{2}\) flux conditions are essential for achieving highly uniform epitaxial wafers. This conclusion is grounded in two main observations. First, at a constant chamber pressure, increasing H\({}_{2}\) flux as a carrier gas enhances the substrate surface's gas flow rate.