The double heterostructure opto-electronic switch equilibrium condition has been formulated in terms of the charge and voltage equations. The dependencies of equilibrium parameters upon variations in doping concentrations in the charge sheet, the barrier layer and the collector layer have been investigated. It is verified under all conditions, that the electron density is much larger than the hole density in the quantum well. The study includes the effects of deionization and free charge in the modulation doping since the small discontinuity values can move the Fermi level close to the conduction band edge. (C) 2002 Elsevier Science Ltd. All rights reserved.