Spatially indirect intersubband transitions of localized electrons and holes at the staggered band lineup In0.52Al0.48As/InP interface

The electronic and crystallographic properties of InAlAs/InP interface grown by metalorganic chemical vapor deposition are studied using double-crystal x-ray diffraction, calorimetric absorption spectroscopy (CAS), steady-state and time-resolved photoluminescence (PL), and Shubnikov–de Haas (SdH) experiments. A high crystalline quality of the interfaces is suggested by the observation of Pendellösung oscillations in the x-ray rocking curves. A two-dimensional electron gas with ns∼6×1011 cm−2 is formed at the InP side of the interface by carrier transfer from the unintentionally doped InAlAs and is directly observed by SdH. Localized hole levels are formed at the InAlAs side of the interface. Spatially indirect optical intersubband transitions between localized electron and hole levels up to n=4 are observed in CAS. The PL and CAS experiments yield an electronic subband structure which is in perfect agreement with results of self-consistent band structure calculations. The 6 K luminescence between localized electrons and holes in their respective n=1 states decays with a time constant of 3.8 ns, considerably larger than what is usually observed at type I quantum wells.