Strong carrier confinement and evidence for excited states in self-assembled InAs quantum islands grown on InP(001)

Abstract

Photoluminescence (PL) and photoluminescence excitation (PLE) experiments are carried out in order to study the electronics states in self-assembled InAs quantum islands (QI's) fabricated on the InP(001) substrate by solid source molecular-beam epitaxy using the Stranski-Krastanov growth mode. The growth conditions of the InAs QI's have been optimized (high growth temperature, low arsenic pressure and growth rate) in order to minimize the island size dispersion. The low-temperature (8 K) PL spectrum of the InAs/InP(001) QI's is characterized by multicomponent transitions. From PLE spectroscopy, we have evidenced excited states associated with a single ground state in agreement with a unimodal size distribution. The full width at half maximum of the ground state PL peak is only 22 meV at 8 K, which reveals a narrow island size dispersion. The integrated PL intensities measured as a function of the temperature have shown a weak intensity decrease between 8 and 300 K. Intensity remains very strong at room temperature, as much as 49% of that at 8 K under nonresonant excitation and up to 90% under quasiresonant excitation. These results are indicating of a strong confinement and/or spatial localization of the carriers in such InAs/InP(001) QI's.