Probing energy barriers and quantum confined states of buried semiconductor heterostructures with ballistic carrier injection: An experimental study

A three-terminal spectroscopy that probes both subsurface energy barriers and interband optical transitions in a semiconductor heterostructure is demonstrated. A metal-base transistor with a unipolar p-type semiconductor collector embedding InAs/GaAs quantum dots QDs is studied. Using minorityor majority-carrier injection, ballistic electron emission spectroscopy and its related hot-carrier scattering spectroscopy measure barrier heights of a buried AlxGa1−xAs layer in conduction band and valence band, respectively; the band gap of Al0.4Ga0.6As is therefore determined as 2.037±0.009 eV at 9 K. Under forward collector bias, interband electroluminescence is induced by the injection of minority carriers with sub-band-gap kinetic energies. Three emission peaks from InAs QDs, InAs wetting layer, and GaAs are observed in concert with minority-carrier injection.