| The goal of this dissertation is to unveil the role of nitrogen incorporation on important processes that shape the high-speed device performance through investigation of the carrier recombination dynamics, nonlinear gain dynamics and carrier capture and escape processes in InGaAsN quantum well lasers. The carrier and gain dynamics are investigated through a comprehensive temperature dependent steady state photoluminescence (PL) and time evolution of PL spectra, ultrafast pump-probe transmission measurement with selective pump and probe wavelengths. The experiments are complemented by theoretical model simulations of the gain spectra. The analysis of the steady state and time dependent PL measurements provided insightful understanding on the effect of nitrogen incorporation on the conduction band effective mass, the electronic structure of the quantum well and the main carrier recombination channels. The electron effective mass (me*) at band edge is found to increase from 0.047m0 to (0.11+/-0.015)m0 after 0.5% of nitrogen incorporation into InGaAs host lattice, using the temperature dependent steady state PL measurement. We show through the gain model analysis that this enhanced me* will result in an increase in transparency carrier density, in the word, threshold current density Ith, but not necessarily decrease the differential gain dG/dN, which is a very important in determining the modulation speed for the device. Through single color pump-probe experiments, carrier heating, two photon absorption (TPA) are found to be the two main factors contributing processes to the nonlinear gain compression. The carrier escape times tauesc is for the first time measured, which is about an order of magnitude smaller in InGaAsN than in InGaAs laser device. These experimental values allow us to understand the impact of nitrogen incorporation on the high-frequency modulation and bandwidth limitations of InGaAsN quantum-well lasers. |
