AlxGa1−xN were grown on (00.1) sapphire and (111) silicon substrates in the whole composition range (0≤x≤1). The high optical quality of the epilayers was assessed by room‐temperature optical absorption and photoluminescence measurements. Layers with higher Al composition are more resistive. Resistive AlxGa1−xN epilayers were successfully doped with Ge and free‐electron concentration as high as 3×1019cm−3was achieved. ©1995 American Institute of Physics.