Investigation of the spatial distribution of silicon donor pairs in a GaAs quantum well

Tunneling through the localized electronic states, which lie below the levels of isolated shallow donors in a weakly silicon-doped GaAs quantum well of a resonance tunneling diode, has been studied. The contour maps of the spatial distribution of the electron probability density of these states have been obtained by means of wavefunction imaging. It has been found that the wavefunctions have axial symmetry and a shape similar to the ground state of a hydrogen molecule, whereas the characteristic sizes of the wavefunctions coincide with the theoretical predictions for the H₂-like states of the donor silicon pairs in the GaAs quantum well with the appropriate binding energies.