Analytical Envelope-Function Theory of Interface Band Mixing

An analytical theory of intervalley mixing at semiconductor heterojunctions is presented. Burt's envelope-function representation is used to analyze a pseudopotential Hamiltonian, yielding a simple $\delta$-function mixing between $\Gamma$ and $X$ electrons and light and heavy holes. This coupling exists even for media differing only by a constant band offset (i.e., with no difference in Bloch functions).