Quantum-Size Effects on the Pressure-Induced Direct-to-Indirect Band-Gap Transition in InP Quantum Dots

We predict that the difference in quantum confinement energies of $\Gamma$-like and $X$-like conduction states in a covalent quantum dot will cause the direct-to-indirect transition to occur at substantially lower pressure than in the bulk material. Furthermore, the first-order transition in the bulk is predicted to become, for certain dot sizes, a second-order transition. Measurements of the “anticrossing gap” could thus be used to obtain unique information on the $\Gamma -X-L$ intervalley coupling, predicted here to be surprisingly large (50–100 meV).