GRADED INGAAS GAAS STRAINED-LAYER SINGLE-QUANTUM-WELL LASER/

A new graded InxGa(1-x)As/GaAs/AlGaAs strained-layer single quantum we ll (QW) laser diode has been proposed and experimentally characterized . Bias-dependencies of valence subbands and maximum optical gains of t he InGaAs QW on the external bias are calculated taking into account t he effects of the valence band mixing and intraband relaxation. Electr on distributions in the conduction bands at threshold bias are also ca lculated by solving the Poisson and Schrodinger equation self-consiste ntly. By a two-step grading of the InGaAs QW compositions, the higher peak value and smaller full width at half maximum of electron distribu tions can be obtained around the QW center even at the large external bias. Moreover, the electron-hole spatial separation is substantially reduced in the graded QW. A graded InxGa(1-x)As/GaAs strained-layer si ngle QW laser diode with x=0.17-0.33 shows lower threshold current den sities by 15% than those of the conventional In0.25Ga0.75As laser.