Optical properties of shallow In/sub 1-x/Ga/sub x/As/In/sub 1-y/Ga/sub y/As superlattices for optoelectronic applications

The authors present detailed photoluminescence, photovoltage, and femtosecond time-resolved luminescence upconversion studies on thin superlattices of type In/sub 1-x/Ga/sub x/As/In/sub 0.53/Ga/sub 0.47/ The sample quality, as derived from sputtered neutrals mass spectrometry data and from the spectral linewidths and excitonic enhancement observed in optical spectra is comparable to very high quality In/sub 0.53/Ga/sub 0.47/As/InP multiple quantum wells. Spectroscopic results agree well with calculations of the materials band structure predicting a mixed type-I/type-II superlattice band structure. Ultrafast carrier capture of charge carriers into the superlattice states has been demonstrated. The high excitonic enhancement and the low confinement energies of holes in this material system make it well suited for fast electrooptic devices.<>