Intrinsic Mechanism for the Poor Luminescence Properties of Quantum-Box Systems.

The poor radiative efficiency in quantum-box luminescence is tentatively explained as an intrinsic effect rather than the usually invoked effect of etch damages. From the recently calculated decreased relaxation rate in zero-dimensional (0D) systems under 100-200-nm lateral quantization, we propose that electrons captured from the barriers in the upper levels of quantum boxes are retained in their cascade to the fundamental states for more than nanoseconds. Due to the mutual orthogonality of quantum states in a box, no luminescence, or much less than in 2D or 3D, can be obtained from these stored electrons with reasonable assumptions for the hole population. Magnetic-confinement experiments in quantum-well lasers support our conclusion. A realistic model at low temperature describes more quantitatively the observed strong decay of the radiative efficiency in quantum boxes and pseudowires with decreased lateral dimensions.