We report electrical and optical characteristics of a Si-doped (Al)GaInAs digital alloy/AlInAs Bragg mirror lattice matched to InP grown by molecular beam epitaxy, A 98.2% reflectivity with a 107 nm stop band width centred at 1.54 mu m is obtained. An average voltage drop of 16 mV per period at a current density of 1 KA cm(-2) is observed for a mean electron concentration of about 5.5 x 10(18) cm(-3). The influence of structural and intrinsic properties of the heterostructure on the electrical resistivity and optical reflectivity is analysed. (C) 2000 Academic Press.2812933