Optical detection of ballistic electrons injected by a scanning-tunneling microscope

We demonstrate a spectroscopic technique which is based on ballistic injection of minority carriers from the lip of a scanning-tunneling microscope into a semiconductor heterostructure. Ey analyzing the resulting electroluminescence spectrum as a function of tip-sample bias, both the injection barrier height and the carrier scattering rate, in the semiconductor can be determined. This technique is complementary to ballistic electron emission spectroscopy since minority instead of majority carriers are injected, which give the opportunity to study the carrier trajectory after injection.