Bound states induced by a single donor in a semiconductor quantum well: A scanning tunneling spectroscopy study

Low-temperature scanning tunneling spectroscopy under ultrahigh vacuum was used to investigate an In0.53Ga0.47As surface quantum well (QW) grown by molecular beam epitaxy. The electronic local density of states (LDOS) was probed with nanometer-scale resolution around native point defects located at the QW surface. In LDOS spectra acquired in the vicinity of a single point defect, a sharp peak was observed near each subband minimum, which indicates the formation of donor bound states. The LDOS peak intensity was measured as a function of distance from the point defect in order to estimate the Bohr radius of the donor bound states.