Temperature Dependence of Dynamic and DC Characteristics of Quantum-Well and Quantum-Dot Lasers: A Comparative Study

Dynamic and static characteristics of high-speed 1.55and 1m wavelength tunneling injection quantum-well lasers and 1m wavelength self-organized quantum-dot lasers, have been measured as a function of temperature. While differential gain of the quantum-well lasers greatly increased with lowering of temperature (by a factor of 50), gain compression increased along with it, resulting in about the same intrinsic damping limit (K-factor) over a wide range of temperatures and only moderate increases in bandwidth (20–35 GHz). This suggests that increase in differential gain alone is not sufficient to improve modulation characteristics directly. Because of the mechanism of gain compression, lasers which are damping limited may not see a large improvement in modulation bandwidth simply by operating at lower temperature. In contrast, the modulation bandwidth of the quantum-dot lasers increased from 5–6 GHz at room temperature to larger than 20 GHz at 90 K. This behavior is explained by considering electron-hole scattering as the dominant mechanism for electron capture in quantumdots. The measured temperature dependence of the K-factor is analyzed with consideration of electron-hole scattering, and the value extracted for the electron intersubband spacing from this analysis, 60 meV, agrees with the theoretically calculated value of 56 meV.