Simulation of QW gain

For a student project, I need to compute and plot the gain of a semiconductor quantum-well.

In my case, I am interested to reproduce the results from Schwartz et al. (Investigation and comparison of optical gain spectra of (Al,In)GaN laser diodes emitting in the 375 nm to 470 nm spectral range). Unfortunately, everytime I try to compute using given formulas, I obtain false result...

So, I am here today to ask if someone can help me to find if there is errors in this article or if someone had already make such a simulation. And in this last case, if a script is available !

Thanks in advance, Dj1312.