Nonparabolic conduction subbands in nanoscale InGaAs/InAlAs quantum wells with photocurrent and transmission spectroscopy

Optical interband transitions of modulation-doped In0.53Ga0.47As/In0.52Al0. 48As multi-quantum wells were clearly observed in the photocurrent and the transmission spectra. The steps of the transitions coincided between the tw o spectra. The effective masses of the conduction subbands were estimated i n fitting the transition energies to an effective mass equation. The masses agreed with the values determined on our previous work with undoped In0.53 Ga0.47As/In0.52Al0.48As multiquantum wells. The effective mass normal to th e quantum well plane was more than 50% heavier than the bulk band-edge mass of InGaAs.