Evaluation of Simulator Incorporating Non-equilibrium Green's Function and Improvement of Quantum Cascade Lasers Output using the Simulator

Abstract

: We applied a simulator incorporating a non-equilibrium Green’s function (NEGF) to quantum cascade laser (QCL) wavelength prediction, and confirmed its validity including its temperature dependence. In addition, the electroluminescence (EL) intensity of the QCL was increased by a factor of 1.4 by including a structure that made the light-emitting layer barrier thin calculated using the simulator. The NEGF is used to calculate the electron density existing in the QCL and the laser gain. To examine the validity of wavelength calculation, we calculated the oscillation wavelengths for the seven types of film structure in the 3 to 9 µm band in our references, and compared them with the experimental results. As a result, the difference between them was well below 0.36 µm. Furthermore, the film structure for increasing the gain was calculated on the basis of the structure reported in one of the references. The gain was increased 1.17 to 1.28 times by reducing the thicknesses of the barriers by 10%. The QCLs with this film structure were prototyped and their EL output intensity was measured. It was confirmed that the EL output intensity output was improved and the film structure design obtained using the simulator was effective.