Schottky barrier photovoltaic detectors based on Si-doped AlxGa1-xN (0 ≤ × ≤ 0.22) have been fabricated and characterized. Samples were grown on basal plane sapphire by LP-MOVPE. Schottky contacts were made with Au. Responsivities are independent of the diode size and of the incident power in the range measured (10mW/m2 to 2KW/m2). The spectral response shows an abrupt cutoff that shifts linearly to higher energy with increasing Al content. A visible rejection of 3 to 4 orders of magnitude is observed in AlxGa1-xN Schottky photodiodes. Device time response is RC-limited, and a minimum decay time as short as 15ns have been estimated in unbiased Al0.22Ga0.28N diodes. This time response can be further reduced by reverse biasing.