Theoretical investigation of gain enhancements in strained In/sub 0.35/Ga/sub 0.65/As/GaAs MQW lasers via p-doping

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Abstract
We present a systematic theoretical investigation of the influence of p-doping on the gain characteristics of strained In/sub 0.35/Ga/sub 0.65/As/GaAs multiple-quantum-well (MQW) lasers, and compare the results with those obtained experimentally from devices with record 30 GHz modulation bandwidths. Experimentally, the combination of p-doping and strain has been found to lead to only a small increase in the differential gain, /spl part/g//spl part/n, but a large decrease in the non-linear gain coefficient, /spl epsiv/; this behaviour has been theoretically accounted for by a doping-induced decrease in the intraband relaxation time, /spl tau//sub in/. The theoretical investigations reveal that the assumption of a constant intraband relaxation time is not sufficient to describe the role of p-doping in the above devices, and highlight the importance of utilizing an appropriate lineshape function for the modeling of high speed laser modulation behaviour.