Contactless electroreflectance of InAs/In_(0.53)Ga_(0.23)Al_(0.24)As quantum dashes grown on InP substrate: Analysis of the wetting layer transition

摘要

Contactless electroreflectance (CER) spectroscopy has been applied to study optical transitions in InAs/In_(0.53)Ga_(0.23)Al_(0.24)As quantum dashes (QDashes) grown on an InP substrate by molecular beam epitaxy. CER resonances related to optical transitions in all relevant parts of the structure, i.e., InAs coverage, In_(0.53)Ga_(0.23)Al_(0.24)As barriers, and the cap layer, have been clearly observed at room temperature. The signal, which is associated with light absorption in the InAs coverage, has been carefully analyzed, and the optical transitions in the wetting layer (WL) quantum well (QW) and QDashes have been identified in CER spectra. It has been shown that measurements of WL transitions and analysis of their energies allow us to determine the band gap discontinuity for the QDash/QDash-barrier interface. It has been found that the conduction band offset for the InAs/In_(0.53)Ga_(0.23)Al_(0.24)As interface is close to ～70%. Moreover, it has been observed that the intensity of the WL transition varies with the cap layer which was used to terminate the QDash structure. The conditions for the observation of WL transitions are discussed in this work.