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<p>Strained layers are used in commercial transistors and diode lasers. It is a pretty important effect and is purely mechanical. Understanding mechanical waves in semiconductors (phonons) is also pretty important too.</p>
<p>To say that mechanical properties of materials is unimportant when it comes to semiconductor physics isn’t quite right.</p>
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<p>Metallurgy is important too when it comes to semiconductors. The process of getting electrons from the outside world into the semiconductors involves picking the right metals and mixtures of metals to do the job.</p>
<p>The old sciences are still good & relevant when it comes to semiconductors. I think that the semiconductor guys just do a good job of advertising about how ‘new’ their technologies are.</p>