Formation of interface states and defects in GaAs–AlxGa1−xAs DH lasers under room-temperature cw operation

Abstract

Experimental results of an investigation on the nature of degradation-induced defects in AlxGa1−xAs–GaAs double-heterostructure injection lasers are presented. The variation of junction capacitance data before and after aging indicates that defects are generated initially at the p-n heterojunction interface and later spread into the active layer as traps. The density of interface states is calculated to be on the order of 1012 cm−2 and the density of traps in the active layer is calculated to be greater than 1017 cm−3. In addition, the carrier lifetime is measured by using both the delay-time and voltage-decay methods. After degradation, the carrier lifetime reduces slightly at the appearance of interface states but shows significant changes when traps are detected in the active layer. An explanation is given and correlated with the threshold-current variation.