The intersubband absorption linewidth has much importance in the operation of quantum well infrared photodetectors (QWIPs) and quantum cascade lasers (QCLs). Here we calculate the intersubband absorption linewidth due to interface roughness scattering, deformation potential acoustic phonon scattering, and optical (intervalley) phonon scattering via the deformation potential, i.e. g phonon. We consider the n-type Si/Si1-xGe x structure. The linewidths are studied for various well widths and different in-plane kinetic energy. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.