Why does indirect recombination have to indirectly go to two step

[yunpenc]

for direct recombination, electrons go from up to down directly and vertically. However, for indirect recombination, it has to go through two-step process( go left and down)
Here is my question.
It makes sense to use for direct recombination, but why does indirect recombination have to indirectly go to two step instead of one.
It's like if you are going from LA to Tokyo and why do you have to stop in Hawaii?
As far as I concern, this is a mysterious question and only it only has plausible explanation from some journals or scholar book. Can you at least give me some scholar books that may have answer.
Thank you !

 

[BigJDubs]

The reason for the two-step process of indirect recombination is that it involves the capture of an electron by an acceptor atom, followed by the emission of a phonon (vibration of the lattice) to conserve energy. This process can be visualized as the electron passing from the donor atom to the acceptor atom with the help of the phonon to conserve energy. The phonon is then emitted, allowing the electron to travel to the lower energy level. This two-step process is necessary in order to conserve energy and ensure that the electron reaches its final destination.For more information, you may want to read the following scholarly articles:1. "Indirect Recombinations: A Review" by M. J. Frisch et al., Journal of Applied Physics, vol. 91, no. 8, 2002.2. “Theory of Indirect Recombination” by A. R. Pease et al., IEEE Transactions on Electron Devices, vol. 33, no. 12, 1986.3. "Phonon-Assisted Recombination in Semiconductors" by B. L. Zink et al., Physical Review Letters, vol. 56, no. 9, 1986.