Minority-carrier confinement by doping barriers

A series of samples with the minority carriers confined within a GaAs epitaxial layer by highly doped regions has been studied. We find an improvement of up to three orders of magnitude in the room temperature radiative effeciency compared with samples without confining layers and that a minimum confining layer thickness of about 300 Å is required. We also find that the radiative lifetime in the layer and the effectiveness of the confinement are reduced in thin active layers owing to diffusion of majority carriers from the barrier regions into the active layer. We deduce that there is a minimum active layer thickness below which confinement by doping barriers becomes ineffective.