Using an analytical model of electron confinement in quantum dots, we have calculated the tunnelling rates for electron quasi-bound states. Schrodinger equation for the disk-shaped system in consideration is readily solved both in the time-dependent and time-independent versions, and the quantitative importance of tunnelling phenomena in low temperature electron emission from quantum dots is revealed. Results of the quantum mechanical analysis are transferred into the device characteristics of common mufti-layer quantum dot hetero-structures. (C) 2003 Elsevier Science B.V. All rights reserved.