N-TYPE DELTA-DOPED QUANTUM-WELL LASERS WITH EXTREMELY LOW TRANSPARENCY CURRENT-DENSITY

It is demonstrated that placing an n-type Te delta doping aside a sing le strained quantum well (QW) is an efficient way to control the initi al carrier concentration in the QW and thus to lower transparency curr ent density, J(tr), while preserving low internal losses. This is in c ontrast with uniform doping of the active area. J(tr) of 11.3 A/cm(2) and threshold current density of 54.4 A/cm(2), which are both the lowe st values reported to date for strained InxGa1-xAs/GaAs semiconductor lasers, were obtained. A somewhat higher injection efficiency is obtai ned when the energy levels are adjusted so that the electrons tunnel f rom the delta well directly into the QW. (C) 1996 American Institute o f Physics.