Defects which led to the degradation of AlGaAs/GaAs lasers were studied by means of deep-level transient spectroscopy and ultrasonic Abrahams-Buiocchi or Doniach-Sunjic etching. It was found that dislocations and deep levels seriously degraded the visible-light lasers. The donor-related deep centers (DX centers) were non-irradiating traps and were attached to the dislocations in n-type AlGaAs. When the laser was in operation, most of the injected carriers collected on the dislocations; together with DX centers. This resulted in degradation of the lasers. The effects of such defects could be avoided by growing an InGaAs buffer layer between the AlGaAs layer and the GaAs substrate.

N.Chen, X.Zhang, Y.Den: Journal of Crystal Growth, 1995, 148[3], 219-22