Temperature dependence of carrier lifetime, recombination, and gain in 1.3 µm InAsP/InGaAsP multiple quantum well lasers

Abstract

In this dissertation we investigate the root causes of the strong temperature dependence of the threshold current in 1.3 μm InAsP/InGaAsP Multiple Quantum Well (MQW) Lasers. We accomplish this through measurements of the carrier lifetime, recombination coefficients, and material gain as a function of temperature. We then analyze the temperature dependence of the threshold current by building a mathematical model of the threshold current using the measured parameters and their temperature dependence. In order to accomplish this goal we developed a new method for measuring the carrier lifetime, which has several advantages over the previously available techniques, and a new analysis for determining the recombination coefficients from the measured carrier lifetime, which is valid for QW lasers. This novel analysis corrects the measured differential carrier lifetime to account for carrier population in both the barrier and separate confinement heterostructure (SCH) regions of quantum well (QW) lasers. The analysis uses information obtained from the measured spontaneous emission spectra to correct the measured lifetime and obtain the intrinsic well lifetime. Once the intrinsic well lifetime is obtained the intrinsic well recombination coefficients can also be obtained. We show that the carrier population in the barrier/SCH layers can significantly affect the measured carrier lifetime and the extracted recombination coefficients. In particular, we show that the Auger recombination coefficient increases with the new QW analysis and has a positive temperature dependence. We also show that this analysis yields material gain parameters that are very different from those obtained with the traditional analysis and much closer to what is predicted for highly strained QW lasers. These differences indicate the importance of accounting for barrier/SCH carriers on the measurement of basic QW laser material properties. The model calculation of the threshold current is found to be in excellent agreement with the experimentally measured threshold current from our deep well InAsP/InGaAsP lasers. This model is then used to show that the dominant cause of the temperature dependence of these lasers is Auger recombination, but that the material gain also plays an important role.