Bandgap and band offsets determination of semiconductor heterostructures using three-terminal ballistic carrier spectroscopy

Among the most important properties of semiconductors are their bandgaps and how the total bandgap difference distributes between the conduction band offset ΔEC and the valence band offset ΔEV at the heterojunction (HJ) interface between two semiconductors. Understanding such properties is crucial for the design of HJ devices. Traditionally, bandgaps are measured mostly with optical spectroscopies such as absorption and photoluminescence (PL). 1. Band offsets are measured electrically by thermionic emission and C-V profiling, optically by absorption and PL, and optoelectrically by photoelectron spectroscopies. However, each of these methods has certain limitations. 2. With a transistor setup, ballistic electron/hole emission spectroscopy (BEES/BHES) utilize ballistic injection of electrons/holes to probe the band offsets of HJs underneath a metalsemiconductor (m-s) interface. 3. However, to obtain the genuine barrier heights, a delta doping is needed to reach a flatband condition across the HJ, which introduces a source of error due to the doping level. 4. Most of the aforementioned methods require separately designed n-type and p-type HJs to measure ΔEC and ΔEV independently, therefore, the results are not necessarily self-consistent.