From the perspective of the law of conservation of momentum, silicon is an indirect transition type semiconductor, its light absorption is limited, and GaAs is a direct transition type semiconductor, and its light absorption capability is strong.

What is the momentum of the wave

In quantum mechanics, the shorter the wavelength, the larger the relative momentum, and the longer the wavelength, the smaller the relative momentum. Here is the Planck constant.

For example, an electron has a wavelength of silicon cell length (character constant S48A), its electron momentum is p=6.63×10-2ergs/5:43×10=122×10 gcm/s; and light with a wavelength of s43m=S430A (green) The fluctuation is 122x10-gcms, which is only 1/1000 of the above electron momentum.