A Unique Photoemission Method to Measure Semiconductor Heterojunction Band Offsets
Qin Zhang, Rui Li, Rusen Yan, Thomas Kosel, Grace Xing, Alan Seabaugh, Kun Xu, Oleg A. Kirillov, David J. Gundlach, Curt A. Richter, Nhan V. Nguyen
We report a unique way to measure the energy band offset of a heterojunction by exploiting the light absorption profile in the heterojunction under visible-ultraviolet internal photoemission. This method was used to successfully determine the band alignment of W/Al2O3/n+InAs/p+Al0.45Ga0.55Sb heterojunctions that are of interest for tunnel field-effect transistors. The barrier heights from the InAs and Al0.45Ga0.55Sb valence band maxima to the Al2O3 conduction band minimum are found to be 3.24 eV ± 0.05 eV and 2.79 eV ± 0.05 eV, respectively, yielding a 0.4 eV ± 0.1 eV offset at the InAs/AlGaSb interface. This novel approach can readily be applied to characterize a wide range of other semiconductor heterojunctions.