Electron transport process in quantum cascade intersubband semiconductor lasers

Detailed self-consistent calculations have been performed of the electron transport and capture aspects of the dynamics of electrically pumped quantum cascade intersubband semiconductor lasers. Specific attention is given to the dependence of the characteristic carrier relaxation times on carrier temperature and density at different applied biases. We have found that the capture and intersubband relaxation times oscillate with increasing electric field. Correlative oscillations can be observed when electron temperature and electron density is plotted as a function of the same applied bias at each energy subband of the laser active region. The temperature and density amplitude are rather less pronounced than those of the relaxations time. Analysis of this typical behavior suggests that the most effective laser structure should work under 70 meV bias.