[en] The A₁-symmetry Raman spectra of berlinite in a broad temperature range, encompassing the α-β phase transition, are reported. The temperature dependence of the lattice mode parameters is presented, particularly concerning the 'soft' mode at ∼220 cm^-1, which exhibits a complex behaviour in the α phase. This is accounted for by coupling with another A₁ mode and two-phonon background in the α phase. It is shown that the soft-mode parameters do not show appreciable discontinuities at the transition. The fact that four Raman active A₁ modes instead of three are observed in the hexagonal β phase can be understood by assuming a dynamical disorder of Al and P atoms over trigonal α-phase sites