MOVPE and characterization of InAsN/GaAs multiple quantum wells

Abstract

InAsN/GaAs multiple quantum wells (MQWs) were grown on GaAs (0 0 1) substrates by metalorganic vapor phase epitaxy (MOVPE) using 1,1-dimethylhydrazine (DMHy) and tertiarybutylarsine (TBAs) as the N and As precursors, respectively. The photoluminescence (PL) peaks of the MQWs clearly show a red shift with increasing DMHy flow rates. This result is opposite to that of the InAsN thin film whose absorption edge shows a blue shift due to the Burstein–Moss (B–M) effect (or band filling effect) caused by the high electron concentration associated with the N incorporation. The red shift of the PL peak is attributed to the huge bandgap bowing appearing with the N incorporation, because in contrast to the result of bulk InAsN, the step-like functional form of the two-dimensional density of states of quantum wells suppresses the B–M effect even in the case of a rise in residual carrier concentration. With increasing DMHy flow rate, the increase of the Stokes shift between the PL and photoluminescence excitation (PLE) peaks was observed. As a result of the excitation power dependence of the PL spectrum, it was found that the Stokes shift is attributed to the compositional fluctuation. These results indicate that the incorporation of the N into InAs in the MOVPE growth of InAsN induces a bandgap reduction due to the bandgap bowing, and the increase of the N content in the InAsN alloy causes the compositional fluctuation.