Determination of band off-sets in MBE grown GaAlAs/GaAs/GaAlAs quantum well heterostructures: application of DLTS and photoluminescence under hydrostatic pressure

It is shown that capacitance spectroscopy on quantum well heterostructures using Schottky barrier diodes, combined with photoluminescence (PL) measurements provides a powerful tool in determining conduction and valence band discontinuities, which are determined to be 72% and 28% of the band gap difference. The electron capture is indicative of a Coulomb's repulsive field. The C-V measurements have also been interpreted to physically locate the position of the well under the surface and the result agrees closely with the value of electrochemical profiling. Further, capacitance spectroscopy under hydrostatic pressure has been used to identify the quantum well and bulk trap emissions. Two electron bulk traps at 0.84 eV and 0.73 eV in the top GaAlAs layer were also detected and the 0.84 eV level is possibly a complex of gallium vacancy and arsenic-gallium antisite defect.