Photocapacitance (PHCAP), deep level photoluminescence (PL), and Hall effect measurements are applied to the liquid phase epitaxially grown n‐Al0.3Ga0.7As crystals followed by an annealing at 900 °C for 1 h under controlled arsenic vapor pressure. Photocapacitance measurements reveal the dominant deep level at Ec-0.5 eV. The Ec-0.5 eV level density increases with increasing applied arsenic vapor pressure during annealing. Deep level PL bands at ∼1.21 and ∼1.36 eV are also detected and the PL band intensity increases with increasing arsenic vapor pressure and the content of doped impurity Te. In conjunction with the results of Hall effect measurements, the origin of the native defects in n‐AlGaAs is discussed in view of the deviation from the stoichiometric composition of the AlGaAs ternary alloy system. © 1996 American Institute of Physics.