R4 is simply a temperature increase compared to R3. This temperature increase improves the doping concentration. However, it does make the epi slightly non selective. This non-selective epi dep results in some noncrystalline regions inside the epi plug. Therefore, we have improved on the doping (while maintaining a similar height) but lost on crystallinity. R5 is a more extreme version of R4 where the crystallinity is sacrificed significantly in favor of higher doping. This is done by lowering the HCl (which lowers the selectivity of the epi process) and also lowering the temperature a bit. The temperature lowering is done to ensure that we get a void free epi dep and therefore, don't need an extra etch back. This enables us to get a void-free epi while at the same time lower crystallinity. However, R5 does have very high doping. Unfortunately, this small epi height is not enough to sustain the downstream PAI + silicidation + Anneal processes. R2 on the other hand shows a slight drop in crystallinity and doping but improved by ~ 4-5 nm in epi height. This drop in crystallinity is a result of non-selective epi growth due to increased temperature. We perform an etch back on this recipe, but the etch-back hasn't etched away all the noncrystalline regions (especially the ones deep inside the epi plug). R3 on the other hand shows a significant improvement (~ 10 nm) in height. The epi deposition is also highly selective thereby ensuring a very crystalline plug. But the dopant concentration has significantly gone down as a result of the lowered Phosphine flow.