Capacitance spectroscopy studies of degraded AlxGa1−xAs DH stripe-geometry lasers

Abstract

The deep‐level transient capacitance spectroscopy (DLTS) technique has been used to study changes in double‐heterostructure (DH) Al_xGa_1−xAs proton‐bombarded stripe‐geometry lasers during accelerated aging at 70 °C. The DLTS spectra of these lasers consist of three dominant peaks: two shallow traps with activation eneriges of 0.31 eV (majority carrier trap) and 0.21 eV (minority carrier trap) and a deep majority carrier trap with an activation energy of 0.89 eV. The deep trap signal changes dramatically during the first 100 h of cw laser operation at 70 °C, while the two shallow traps change in concentration by only about 10–20%. This deep trap signal increases by over an order of magnitude in lasers of moderate reliability (∼10³ h at 70 °C) but is observed to decrease in lasers with very long lifetimes. It is shown that this deep level is introduced by the proton damage and is initially located at the interface between the proton‐damaged layer and the N‐ternary waveguide layer. Finally, studies of the shift in energy of this deep level as a function of aluminum fraction in the Al_xGa_1−xAs waveguide layer show that this trap is very likely the same as the E3 radiation damage trap. This correlation is significant since the E3 defect is known to be mobile at room room temperature under conditions of electron‐hole recombination and a very efficient nonradiative center in p‐GaAs. If such a center were to move into the p‐type active region, it would be a prime candidate for the source of spatially uniform degradation.