The epi height/volume forms the first corner of the epi trilemma. Epitaxial growth in a deep, narrow trench is a thermodynamically unstable process. The instability comes due to the fact that the epi has a high aspect ratio, which is growing in a towering fashion over the small surface area. This makes the epi growth susceptible to strain relaxation. . These [111] facets are incredibly low in surface energy and are highly stable. Therefore, they won't sustain any more epitaxial growth. This brings the epi growth to an abrupt halt. This selfsaturating behavior of epitaxial growth can be seen in fig V. The epitaxial structure height increases with dep time till approximately 450-500 sec. After which, the deposition comes to a halt and no matter the increase in dep time, we hardly see any increase in epi height. This self-saturating growth of epi arises due to the instability caused by the tensile lattice strain which forces epi to form facets. Therefore, there are two ways to increase the epi height 1) Lower the doping 2) Lower crystallinity.