Reduced electron-phonon relaxation rates in quantum-box systems: Theoretical analysis

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Abstract
Reasons for the reduced electron-phonon relaxation arising in the conduction band of zero-dimensional quantum-box (QB) systems when level separation is of the order of 1 meV or larger are explained. Relaxation rates are calculated using approximations of the electron-phonon interaction matrix element between two given levels. A threshold QB energy-level separation and a threshld QB size for reduced relaxation are then deduced. To deal with the multilevel situation encountered in flat square boxes with two dimensions much larger than the third one, it is shown that the energy-independent density of states in a given subband translates into a Poissonian distribution of the level separation. This statistical approach is developed to predict the occurrence of relaxation bottlenecks along a cascade of levels in intra- and intersubband transitions cases. DOI: http://dx.doi.org/10.1103/PhysRevB.51.13281 © 1995 The American Physical Society