CARRIER CONCENTRATION SATURATION OF DOUBLE SI DOPING LAYERS IN GAAS

Doubly Si delta-doped GaAs samples with different spacer thickness are grown by molecular beam epitaxy. By adopting a growth temperature as low as 400 degrees C, a ''true'' delta-doping profile is realized and confirmed by Shubnikovde Haas measurement. A depopulation of sheet car rier concentration is observed as the two layers approach each other. The carrier concentration saturates in such a way that the depth of th e self-consistently calculated Hartree potential is kept constant at a round 235 meV. Since carrier concentration saturation due to structura l reasons remains unchanged in these structures, the pinning of Fermi level suggests a dominant electronic saturation mechanism most likely through the population of DX center states.