Temporal stability and absolute composition issues in molecular beam epitaxy of AlGaAs/GaAs THz QCL I. S. Vasil’evskii, A.N. Vinichenko, M.M. Grekhov, V.V. Saraykin, A.N. Klochkov, N.I. Kargin, R.A. Khabibullin and S.S. Pushkarev EPJ Web Conf., 195 (2018) 04006 Published online: 23 November 2018 DOI: 10.1051/epjconf/201819504006