Aluminium doped ZnO (AZO) alloy films produced by atomic layer deposition (ALD) are analysed by glow discharge optical emission spectrometry (GD-OES). A measurement procedure is established, to determine simultaneously thickness, mean chemical composition and refractive index of homogeneous films using GD-OES and profilometry measurements. The GD-OES measured Al contents of the AZO films lie below those expected for the realised ALD cycles. Determined refractive indices are of the same accuracy as ellipsometry measurements and are dependent on the film composition as well as on the wavelength of the spectral lines used for analysis. The findings support the use of GD-OES as an analysis technique in the development of photovoltaic thin films.