There are a few key reasons why silicon is used more often than germanium in semiconductor devices.
First, silicon can be found more abundantly in nature compared to germanium. This means that it is less expensive to use silicon as a starting material for semiconductor devices.
Second, silicon has a much higher melting point than germanium. This makes it possible to create very pure silicon crystals, which are necessary for semiconductor devices.
Third, silicon can be used to create very small and intricate structures using advanced lithography techniques. This is not possible with germanium.
Finally, silicon has better electrical properties than germanium, which makes it a better choice for semiconductor devices.