Band offsets of InGaP/GaAs heterojunctions by scanning tunneling spectroscopy

Scanning tunneling microscopy and spectroscopy are used to study InGaP/GaAs heterojunctions with InGaAs-like interfaces. Band offsets are probed using conductance spectra, with tip-induced band bending accounted for using three-dimensional electrostatic potential simulations together with a planar computation of the tunnel current. Curve fitting of theory to experiment is performed. Using an InGaP band gap of 1.90 eV, which is appropriate to the disordered InGaP alloy, a valence band offset of 0.38±0.01 eV is deduced along with the corresponding conduction band offset of 0.10±0.01 eV (type I band alignment).