Dopant and carrier profiling in modulationhyphen;doped GaAs multilayers with crosshyphen;sectional scanning tunneling microscopy

摘要

We report the direct measurement of dopant and carrier density profiles in GaAs (001) modulationhyphen;doped structures using crosshyphen;sectional scanning tunneling microscopy. On ultrahighhyphen;vacuumhyphen;cleaved crosshyphen;sectional (110) GaAs surfaces, individual electrically active dopants are observed as hillocks in the top several surface layers, and the tiphyphen;sample separation is found to be sensitive to the carrier concentration. In structures where the conventionally measuredphyphen;type dopant concentration varied from 1times;1018to 1times;1019cmminus;3the density of such dopant hillocks varies accordingly and the tiphyphen;sample separation changes by 0.1 nm.