Highly conductive and transparent aluminium-doped ZnO (ZnO:Al) thin films have been prepared on low temperature substrates by chemical beam deposition (CBD). The ZnO:Al thin films were prepared by intermittently and alternately feeding source gases : diethylzinc (DEZ), water (H2O) and triethylaluminium (TEA) or trimethylaluminium (TMA). The stoichiometry of the ZnO films was controlled by changing the pressure of either the DEZ gas or the H2O gas introduced into the chamber. The carrier concentration of the films was successfully controlled by changing either the TEA (or TMA) gas pressure or the ratio of TEA (or TMA) to DEZ introduced during one cycle. A ZnO:Al film with a resistivity as low as 3.4 x 10(-4) Ohm cm and a transmittance above 85% in the visible range was prepared at a substrate temperature of 150 degrees C under optimized Al-doping conditions. A sheet resistance of 60 Ohm/square was obtained in a ZnO:Al film 60 nm thick prepared at a substrate temperature of 150 degrees C. The deposition mechanism of ZnO films is discussed.