Direct evidence for group III atoms migration in aged 980 nm InGaAs/AlGaAs pump lasers

Low Temperature–Spectrally Resolved Cathodo‐Luminescence (LT‐SRCL) and Cathodo‐Luminescence Imaging (CLI) have been used to study the effects of high temperature and high current density aging on 980 nm InGaAs/AlGaAs pump lasers. The aged lasers show a characteristic evolution of the luminescence band related to a thin (≅ 25 nm) InGaP etch‐stop layer: a blue‐shift of several meV is observed, together with a rather strong increase in the luminescence intensity. The blue‐shift is related to an increase in the disorder of the InGaP alloy while the strong increase of the intensity may result from a different localization of the injected carriers due to a modification of the potential profile. A possible microscopic mechanism for the disordering of the InGaP layer is discussed, based on the migration of either p‐type impurities (Zn, in this case) or excess group III interstitials.