Illumination of the substrate during growth by molecular‐beam epitaxy (MBE), known as photoassisted molecular‐beam epitaxy, has been investigated for (111)B, (211)B, and (100) oriented growth of HgCdTe on CdZnTe. The results of this investigation indicate that photoassisted MBE of HgCdTe results in significant improvements in structural perfection. HgCdTe epilayers with average double‐crystal x‐ray diffraction full widths at half‐maximum of 4 cm−2 have been observed. The structurally perfect HgCdTe epilayers also exhibit outstanding electrical properties after n‐type annealing. Hg‐based multilayer structures have also been grown by photoassisted MBE at North Carolina State University. HgCdTe–CdTe superlattices grown by this technique are comparable in structural quality to III–V superlattices. Hg‐based double‐heterojunction structures, suitable for fabrication of injection lasers, have also been grown. These latter structures exhibit bright IR photoluminescence.