Quantum confined Stark effects of heavy hole subbands in In/sub 0.53/Ga/sub 0.47/As/In/sub 0.52/Al/sub 0.48/As multi-quantum well structures using photocurrent spectroscopy

Infrared photocurrent spectra in In/sub 0.53/Ga/sub 0.47/As/In/sub 0.52/Al/sub 0.48/As multiquantum wells were measured at room temperature under an external electric field. The interband photocurrent spectra showed a number of clear steplike structures due to two-dimensional subbands accentuated by free exciton states, in 10-nm-thick InGaAs quantum wells (QWs) separated by 10-nm-thick barriers. Energies of the confined states in QWs near zero field were extrapolated from higher field and shown to be proportional to the squared quantum numbers of heavy hole (HH) subbands and conduction subbands. Contribution of light hole (LH) was discriminate by a separate experiment under a tilted polarized light. The HH-related peaks were most sensitive to the bias field because the quantum confined Stark effect (QCSE) was stronger in HH subbands. Model calculation precisely revealed that an allowed LH transition could change into a forbidden HH transition by an electric field. Nonparabolicity of HH mass normal to the QW plane was surmised small.