Measurement of quasibound states in semiconductor heterostructures using ballistic electron emission spectroscopy

Ballistic electron emission spectroscopy (BEES) has been used to measure the quasibound states in a series of Ga1−xAlxAs heterostructures. These structures include a Ga0.8Al0.2As single-barrier device and two complementary electron-wave Fabry–Perot quantum interference filters. By utilizing the BEES second-derivative spectrum, which is a measure of the electron transmittance function of the buried heterostructure, we have been able to determine accurately the characteristics of quasibound states for devices designed and optimized to show specific resonances (Fabry–Perot electron-wave filters) and for devices neither designed nor optimized to show interference effects (single-barrier structure). The measurements reproduce accurately the calculated zero-bias transmittance function of the electron-wave filters and clearly demonstrate the unique capabilities of the technique for providing crucial information that is not available from other techniques.