Semiconductor heterostructures have great ability to bind carriers and the potential to produce high power terahertz radiation. However， the intensity of terahertz radiation is substantially reduced， due to the interference effects of incoherent oscillations of plasma in the heterostructure. Thus in the AlGaAs ） multilayer heterostructure， it is able to adjust the absorption coefficient of the narrow band-gap layer by adjusting the aluminum molar fraction， which makes the excitation carriers number in each narrow band-gap layer approximately the same， achieving the goal of almost completely eliminating the interference effects. Based on the AlGaAs multilayer heterostructure terahertz radiation model， the properties of broadband terahertz radiation are studied with the numerical calculations， the quantitative relationships between the pump laser pulse width and the generated terahertz pulse are obtained， and the influence of pump laser pulse parameters on the parameters of generated terahertz pulse is also analyzed. This study provides a reference for the development of broadband terahertz radiation sources based on the semiconductor.