best semiconductors

[Rothiemurchus]

If cost wasn't an issue, what would semiconductors be made from to maximise their efficiency,useful lifetime etc?

[Manchot]

It really depends on the application. Silicon, for example, isn't just cheap: it also has a native oxide that can be easily grown without forming surface states. III-V compounds, while generally faster, don't have good native oxides, and make poor-quality FETs. On the other hand, III-Vs are great for HBTs.