Doping-type dependence of turn-on delay time in 1.3-μm InGaAsP-InP modulation-doped strained quantum-well lasers

The dependence of turn-on delay time on doping type in 1.3-μm InGaAsP-InP modulation-doped (MD) strained quantum-well (QW) lasers is theoretically investigated, based on the detailed band structure model including the band mixing effects. It is found that the turn-on delay time in n-type MD lasers is reduced to 1/4 that of undoped lasers due to both a lower threshold current and a reduced carrier lifetime. The reduction of the delay time is smaller in p-type MD lasers, however, because of the increased threshold current. These results show that the n-type MD-QW lasers are superior for high-speed modulation under zero-bias conditions.