Spin exchange between a quantum well and the donor layer in Si/Si1-xCx

Electron-spin-resonance (ESR) data from modulation-doped Si/Si1-xCx heteros tructures are reported. The experiments at high ESR frequency (94 GHz) and corresponding high magnetic field (3.5 T) enabled us to separate the ESR of the conduction electrons in the quantum well from the ESR of the phosphoro us donors in the doping layer. At temperatures above 20 K a thermally activ ated electron-exchange process between the quantum well and the donor layer is observed. The effective activation energy of this process is approximat e to 19 meV. The g factors of the conduction electrons and of the P donors were determined with high absolute accuracy. [S0163-1829(99)02319-X].