The most recent wave of digital transformation reshapes nearly all aspects of human society and is currently driven by innovations in areas such as AI and machine learning, AR/VR, autonomous driving, cloud and edge computing, 5G etc. All of these applications require emerging technologies across various fields such as high performance computing (e.g. advanced CMOS), storage, high-bandwidth data communication (Photonics, Analog/RF circuits) and sensing (lasers, detectors...). Undoubtedly, the requirements of these diverse technologies cannot be met by a single semiconductor material but instead demand the heterogenous integration of different materials such as (Si)Ge alloys, III-V compounds like (In)GaAs, In(Al)As, (In)GaSb etc. However, the integration of these materials on Si substrates is particularly challenging due to the large lattice mismatch leading to plastic relaxation and hence extended crystalline defects such as dislocations as well as stacking faults and nanotwins. Such extended defects can degrade the material properties, lead to significantly increased leakage or dark currents and moreover cause secondary effects such as dopant and impurity segregation, thereby severely limiting device performance and reliability. Hence, defect metrology enabling a precise and statistically relevant characterization of these heterostructures with low detection limit is crucial. In this presentation we will demonstrate that electron channeling contrast imaging (ECCI) can close this apparent metrology gap by enabling a fast, reliable and non-destructive assessment of the density and nature of extended crystalline defects in confined semiconductor heterostructures using a scanning electron microscope. After discussing the fundamental aspects of the technique, we will present its direct application toward a number of different material systems and structures. In this context we will highlight the technique’s capability to (1) understand strain relaxation and defect formation mechanisms at the nanoscale and, moreover, (2) assist process engineers to unravel the crystalline quality of their materials thereby facilitating process development and device fabrication.