A carrier transport model to explain the high-frequency response in high-speed MQW lasers is described. The ambipolar approximation, which is unsuitable for dealing with the high-speed carrier dynamics in MQW structures, was not adopted for small-signal analysis. The carrier transport effect can be characterized by four time constants: the electron transport time, τbmn; the hole transport time, τbmp; the electron escape time, τwbn; and the hole escape time, τwbp. The frequency response was interpreted as the sum of the constant response term due to the fast electron current and the roll-off term due to the slow hole transport time. The ratio of the electron contribution to the total response was proportional to the ratio of electron contribution to the total differential gain, ξ, and reciprocally proportional to χn0= 1 + τbmn/τwbn. The value of ξ was calculated to be about 0.5 for typical MQW lasers. The roll-off frequency is mainly determined by . The ratio χp0= 1 + τbmp/τwbpaffects the resonant frequency and the damping rate in the high-bia
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