A novel external-cavity semiconductor laser faced to butterfly packaging which can generate wide bandwidth chaos is designed, and the influences of feedback ratio, injection current ratio and carrier lifetime on dynamic performance of the designed structure are investigated. Numerical simulation results demonstrate that diversely dynamical states including the stable state, as well as the so-called period-one, and chaotic states can be observed when the feedback ratio is adjusted or the injection current ratio is increased. The relaxation oscillation frequency of the external-cavity semiconductor laser rises with the increasing injection current ratio or the decreasing carrier lifetime. So it is much easier to generate chaotic signal with effective bandwidth of 70 GHz when the relaxation oscillation frequency and oscillation frequency of the external-cavity are at high level. The mechanism to generate such a chaos with wide bandwidth is analyzed, which provides a new source of entropy for the generation of random number. In addition, we use the relaxation oscillation of laser to cover time delay characteristics of feedback when the feedback is weak, and analyze the influence of feedback time delay on the dynamics of oscillation frequency of the external-cavity.