Reduction in the concentration of D X centers in Si-doped GaAlAs using the planar doping technique

Whereas the concentration of DX centers in Si-doped GaAlAs is nearly independent of the molecular beam epitaxy growth conditions when conventional bulk doping is used, we have discovered that it can be strongly reduced in the case of planar doping. Most interesting is the fact that this reduction is more effective at a high doping level. At an electron density of 2×1013 cm−2 per doping plane [3% of the atomic density of a (100) oriented GaAlAs surface] we observe a nearly complete disappearance of these centers. A possible origin of this unexpected effect is proposed.