Spectroscopic study of Ga-In-P based self-organized lateral superlattices
This paper reports polarization and temperature dependent contactless electroreflectance (CER) and photoluminescence (PL) study of strain compensated short period superlattices on GaAs(001) substrates which show self-organized lateral composition modulation (LCM) in the form of alternate In/Ga rich regions along the [110] direction in the (001) plane. The LCM related PL peak position is at a lower energy as compared to the corresponding feature in the CER spectrum and the difference is found to be the same as the activation energy for thermal quenching of the PL signal. These results have been explained by suggesting that the PL signal arises mainly from recombination of carriers localized at potential fluctuations (In rich regions with excessively high In concentration) within the lateral superlattice (LS) structure that is formed due to the LCM while the CER feature arises from transitions between the minibands of the average LS structure. The PL signal is quenched due to thermal excitation of the carriers from these excessively In rich regions into the minibands. The LS band gap energy is accurately determined and its implication for the random alloy model used to describe the electronic band structure of such systems is discussed. The temperature dependences of critical point energies have also been measured and analysed.