Below-bandgap photoluminescence from GaAs

Abstract

The below‐bandgap photoluminescence (PL) from semi‐insulating (s.i.) GaAs is investigated. It is found that various electronic states that give rise to near‐infrared (NIR) PL peaks are generated through processes that are standard for epitaxial growth of InAlGaAs structures on (001) GaAs substrates. Moreover, the PL signals from these states overlap with those from InAs quantum dots, wetting layers, and InGaAs structures, complicating the design of devices for telecommunications or intermediate band solar cells. The spatial positions of the various defects are also investigated by below‐gap excitation and back‐illuminated PL measurements. The possible identities of the defects are also presented. The present results provide guidelines for distinguishing the desired electronic states from thermal treatment‐induced defect states.