Dependence of threshold current on the number of wells in AlGaAs‐GaAs quantum well lasers

GaAs‐AlGaAs multiple quantum well injection lasers have been grown by molecular beam epitaxy with different numbers (N) of uncoupled GaAs wells 25 A wide symmetrically disposed about the center of a 4000‐A‐wide waveguide. The devices emit at about 770 nm and for N=4 the broad area threshold current density is 1.1 kA cm−2. The threshold current increases with increasing N (2<N<40) and this can be accounted for by changes in the optical confinement factor and the active ‘‘volume,’’ which implies that changes in capture probability with N in this structure are small.