There are companies which develop leading edge products that depend on lasers, LEDs or gallium nitride power transistors.
If China really cuts the exports of gallium and germanium, then such companies might have to reduce the volume of their production and to raise prices, which would lead to lower sales. Lower sales would cause lower profits, so maybe less money will be spent on research.
Gallium and germanium are widespread, but their extraction processes are extremely expensive.
A shortage would rise their prices, which would stimulate the creation of new mines and refining plants. However, that would require a few years. China has just been hit by a new wave of US sanctions that will make difficult for them to continue the production of some semiconductor devices, but they should also be able to become self sufficient in a few years.