Probing the quality of interfaces, dopant distribution, layer thicknesses, and crystalline quality in buried layers and volumes has been critical for developing new semiconductor materials and devices. These challenges have been addressed by a combination of techniques based on Electron Microscopy (EM) and Atom Probe Tomography (APT) for new transistor architecture1. We have extended their applicability to materials and devices developed for quantum information processing2 and photonic applications3-5 with significantly larger dimensionsaddressing the need for atomic scale metrology of heterostructures with thicknesses of up to several micrometers (Fig. 1).For example, CMOS compatible Quantum cascade lasers based on superlattices of n-type Ge/Si1-xGex QWs are predicted to be operable at room temperature and to emit throughout the entire THz spectral region (300GHz-1THz, 1mm-30µm) solving a key challenge in solid-state optoelectronics5. In a QCLs charged carriers travel through the superlattice alternating between emitting radiation when traversing between the subbands of the superlattice and tunneling from one period of the cascade to the next3,5. In order to act as a laser, the underlying material structure has to allow for coherent radiation, population inversion, efficient tunneling and propagation of the emitted radiation. This implies the need to develop the growth of superlattices up to 1000s of periods that are highly uniform in thickness, strain compensated, of high crystalline quality, and have well controlled doping levels and steep interfaces reaching a thickness of several micrometers3,5.Here we will show how we combine X-Ray Diffraction, EM and APT to characterize Ge/Si1-xGex superlattices and SiGe-, GeSn- and SiGeSn heterostructures to investigate interface properties, determine layer thicknesses, and map the distribution of dopants and isotopes6 in structures with micrometer dimensions. These studies are of compelling importance to enable a progressive improvement of these material systems towards their respective applications.