On the relationship between electrical and electro-optical characteristics of InAs/InP quantum dot lasers
This paper addresses the electrical and electro-optical characteristics of InAs/InP quantum dot (QD) laser diodes operating under continuous wave in the temperature range of 285 K to 353 K. Experimental data together with a model lead to an identification of the current flow mechanism in all the important drive regimes: very low bias (pre radiation regime), the exponential region of the current-voltage (I-V) curve, and in the nonlinear range where spontaneous and stimulated emission take place. The analysis discriminates among bias regions where the influences of the QD or the optical confinement layers dominate. Additionally, parameters and non-nonlinear processes under injection into the active region are described here for the first time. A high level injection (spontaneous, as well as stimulation emission regimes) results in non-linear I-V characteristics. Above the threshold, the recombination rate increases due to rapid “pinning” of the quasi-Fermi levels leading to an anomalous kink of the power exponent voltage characteristics. This manifests itself as a non-linear differential resistance increase even at elevated temperatures, up to 353 K. Capacitance voltage measurements reveal some peculiarities, namely, well defined capacitance peaks related to the QDs, hysteresis, and a low frequency negative capacitance phenomenon which enhance the laser potential functional capability.