We analytically describe the concept of broadband second-harmonic generation in the near-IR region in an isotropic tapered semiconductor slab made of zinc selenide. A computer-aided simulation has been carried out to determine the possibility of generating broadband second-harmonic intensity when broadband fundamental laser radiation is allowed to undergo total internal reflection inside the tapered semiconductor slab. The simulated results indicate an extremely broad spectral bandwidth of 557 nm centered at 4.05 µm (3.812 to 4.369 µm) in a 10-mm-long slab with a conversion efficiency of 0.02%. The losses due to absorption and surface roughness of the semiconductor material have been considered in the analysis. The effects of variations in the temperature, length, and tapering angle of the semiconductor slab have been studied for the generated second-harmonic radiation.