A light emitting device including a substrate transparent at the emission wavelength and an active layer structure formed on such substrate, in which the thickness of the substrate is 75 .mu.m or less, and/or a layer for suppressing spectral-intensity-modulation due to the substrate-mode is provided between the substrate and the active layer structure. Such device can suppress the spectral-intensity-modulation due to the substrate-mode, which is observed for the case the substrate is transparent at the emission wavelength, to thereby provide a light emission device excellent in linearity of the current-light output characteristics, and to thereby improve the coupling characteristics with an external cavity.