Carrier Concentration Saturation of Double Si Doping Layers in GaAs

Doubly Si δ-doped GaAs samples with different spacer thickness are grown by molecular beam epitaxy. By adopting a growth temperature as low as 400° C, a "true" δ-doping profile is realized and confirmed by Shubnikov-de Haas measurement. A depopulation of sheet carrier concentration is observed as the two layers approach each other. The carrier concentration saturates in such a way that the depth of the self-consistently calculated Hartree potential is kept constant at around 235 meV. Since carrier concentration saturation due to structural 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.