This article presents an overview of trends and progress in group IV heterostructures for optoelectronics. The outlook is good in electronics because the commercialization of SiGe/Si heterotransitors is proceeding nicely. However, the pace of progress is slower in SiGe/Si photonics. This article covers five innovative topics in an effort to enhance the development of heterostructure photonics : (1) band-gap studies of SiGeC, an alloy that can be lattice matched to Si, (2) direct-band-gap, strained heterostructures of GeSn upon GeSi/Si, (3) silicon-based quantum-well intersubband lasers (ISBLs) including SiGe/Si quantum-cascade, Raman, and inversionless ISBLs, (4) 1.5 mu m ISBLs based on Si quantum wells with high barriers, such as heterosystems of Si/ZnS, and Si with SiO2/Si strained superlattice barriers, and (5) low-cost substrates of 3C SiC upon SiO2/Si, a platform for SiC heterodevices and for InGaN/AlGaN heterodevices.