Temperature dependence of carrier dynamics in an inhomogeneous array of quantum dots

Abstract

A model portraying the carrier dynamics for an inhomogeneous array of quantum dots (QDs) interacting with a number of photon modes is presented. The model treats an ensemble of QDs with one confined level coupled to a wetting layer or quantum well level and explicitly considers only the electrons. The model is derived by numerically solving a set of rate equations that includes the inhomogeneity of the dot size, multimode photon modes and temperature dependence. Explicitly the inhomogeneous size distribution is included within a inhomogeneous broadening parameter and the temperature dependence within the homogeneous broadening parameter as well as carrier thermal escape. This is similar to the well-known Sugawara model 1 but in the Sugawara model the carriers are assumed to occupy the inhomogeneous quantum dots equally at all temperatures. Experimental and theoretical work in ref.(2) and (3) believes this is true only for a low temperature regime. Above the temperature where a global minima exists, Fermi-Dirac statistics have been used. This results in different gain and lasing behaviour for higher temperatures from those calculated using the Sugawara model.

Mode Amplification in Inhomogeneous QD Semiconductor Optical Amplifiers

“…In our case I tr = 1.2 mA. (*More recent comparison of the experimental result to the modelling result can be referred to at Wong (2006)). …”

“…(b) Assumption of carrier filling which assumes a quasi-equilibrium carrier distribution. This reflects characteristics of carriers in the higher temperature region (Zhukov et al 1997, Jiang andSingh 1999;Wong et al 2004). The resonant energy (or frequency) is normalized to 0 and the detuning refers to the inhomogeneous dot size distribution where −E j (−ω j ) represents the deeper dots and +E j (+ω j ) represents the shallower dots.…”

“…The assumption of equal carrier filling, as illustrated in Fig. 1(a), corresponds well to the low temperature operating regime where carriers have a short diffusion path going into a random QD and once being captured, the electron recombines from this dot due to the suppression of carrier-carrier scattering at such temperature (Zhukov et al 2004;Wong et al 2004). In the high temperature regime, the QDs become more coupled as carriers scatter via the homogeneous broadening and via the WL.…”