2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/30116We introduce an elementary model for the electrostatic self-consistent potential in a two-dimensional electron gas. By considering the perpendicular degree of freedom arising from the electron tunneling out of the system plane, we predict a threshold carrier density above which this effect is relevant. The predicted value agrees remarkably well with the onset for the insulator to quasi-metallic transition recently observed in several experiments in SiO2-Si and AlGaAs-GaAs heterojunctions.REVTeX 3.0, 8 pages, 1 Postscript figure includedMesoscale and Nanoscale Physicstext