Anomalous threshold current and time delays in index-guided AlxGa1−xAs-GaAs quantum-well lasers

Abstract

Anomalous threshold current (Ith) variation with temperature and with pulse length, and large delays (up to 6 μs) between excitation and the turn-on of stimulated emission are observed in index-guided AlxGa1−xAs-GaAs quantum-well heterostructure (QWH) lasers. These effects are found in laser diodes incorporating ‘‘spike’’ doping layers (δ-Mg and δ-Se) within the QWH active region and that are fabricated via laser-assisted Si impurity-induced layer disordering. The introduction of contaminants during the localized melting and regrowth of the laser-induced layer disordering, and the effect of these impurities (or defects) with the active region ‘‘spike’’ doping create traps. The traps cause Ith to increase (not decrease) at lower temperature and at shorter current pulses, and cause time delay in turn-on of the operation.