Tunnel field-effect transistor heterojunction band alignment by internal photoemission spectroscopy

The electron energy band alignment of a metal-oxide-semiconductor tunnel field-effect transistor heterojunction, W/Al2O3/InGaAs/InAs/InP, is determined by internal photoemission spectroscopy. At the oxide flat-band condition, the barrier height from the top of the InGaAs/InAs valence band and the top of the InP valence band to the bottom of the Al2O3 conduction band is determined to be 3.5 and 2.8 eV, respectively. The simulated energy band diagram of the heterostructure is shown to be consistent with the measured band alignments if an equivalent positive charge of 6.0 × 1012 cm−2 is present at the Al2O3/InGaAs. This interface charge is in agreement with previously reported capacitance-voltage measurements.