Interest in broken-gap, type-II heterostructures for optoelectronic applications is predicated largely on their promise as infrared lasers, detectors, and modulators appreciably outperforming conventional devices. Cryogenic imaging arrays based on these structures are projected to perform with higher detectivities and/or at higher operating temperatures than competing systems based on HgCdTe or extrinsic materials. Lasers in the 3-5μm spectral band are expected to operate at or near room temperature with significant output powers, and modulators with unusually low insertion losses and high dynamic range have been proposed. Brought to maturity, applications of such devices would be numerous, ranging from environmental monitoring systems to short-link, high bandwidth optical communications.