Abstract

To date, several papers have reported that the optical qualities of GaAs/AlGaAs quantum wells (QWs) are improved by introducing such prelayers as multiple quantum wells (MQWs) and GaAs/AlAs short-period superlattices (SPSLs) between the QW layer and the substrate.^1~3) Therefore, it has become popular to introduce MQWs or SPSLs in diode laser structures with SQW active layers expecting low threshold current operation. However, a systematic and quantitative analysis of the role of those ultrathin structures on the improvement in lasing threshold current of QW lasers has not been performed yet. This paper describes the results of a timeresolved photoluminescence (PL) study on the role of SPSLs, which were introduced as waveguide layers, in place of AlGaAs alloy layers, for single quantum well (SQW) lasers and brought the reduction in lasing threshold current by a factor of 4~6.

© 1988 Optical Society of America