2-DIMENSIONAL LIMITATIONS WHEN INCREASING THE SI-CONCENTRATION FROM DELTA-DOPING TO THIN SI-LAYERS IN GAAS

Silicon layers, embedded in GaAs extending from a low delta-doping con centration up to 6 monolayers (ML), were grown at 500 degrees C and in a delta-doped region at 580 and 630 degrees C. The structures were ma inly characterised by Hall effect measurements and secondary ion mass spectroscopy. For doping concentrations below 2 x 10(12) cm(-2), the m ajority of the carriers were trapped. At 4 ML thickness, a relaxation of the Si-layer was detected which resulted in enhanced diffusion. Fur ther, an assessment of diffusion as a function of growth temperature a nd doping concentration is made. Finally. a model is proposed to asses s the minimum diffusion as a function of growth temperature.