Abstract

Gradual degradation in semiconductor lasers is caused by the creation and migration of point defects which require jumping of atoms from their initial position to disordered ones (with activation energy E_a of a few electron volts). The injection of a nonequilibrium electron-hole plasma may increase the probability of structural changes and reduce their activation energy by δE ≃ F_c − F_v through nonradiative recombination¹ (F_c and F_v are the quasi-Fermi levels). Such enhancement is possible only if the recombination is synchronized with the atom jump event, and the released energy δE is localized around this atom. In the present model, such synchronization is inherent: the fluctuating atom forms a transient point defect which behaves as a nonradiative recombination center of lifetime δ_τ ≃ 10⁻¹³ − 10⁻¹²s. Free carriers are trapped at these centers leading to synchronous release of localized energy δE. This model is based on the kinetic many-body theory of short-lived large energy fluctuations of atoms.²,³ The laser degradation rate K is given by K = K_o exp[−(E_a − δE)/kT] with K_o and δE expressed in terms of the laser parameters (carrier concentration, energy gap, defect concentration, etc.) Calculated laser lifetimes are in good agreement with experimental data.

© 1988 Optical Society of America