Nonparabolic tendency of conduction subbands in In0.53Ga0.47As/In0.52Al0.48As multi-quantum wells by photocurrent spectroscopy

In In_0.53Ga_0.47As/In_0.52Al_0.48As multi-quantum wells containing 5, 9.4 and 20 nm well widths, interband transitions were clearly observed in photocurrent difference spectra. Using a new assumption that electron effective mass is 0.041 m₀ at the bottom of a conduction quantum well and as much as one of bulk at the conduction bandedge and varies smoothly toward higher energy, the energy dependence of the effective mass was sufficiently considered even as small eigen-energy at small quantum-number. After fitting experimental transition energies to the envelope function model, nonparabolicity of the electron effective mass explicitly was determined as a function of energy in a direction normal to quantum well layers. The electron effective mass smoothly increased from 0.041 m₀ to 0.08 m₀ in the conduction quantum well at room temperature.