The article investigates the detrimental effect of nonuniform and uniform crack distributions over a solar cell in terms of open-circuit voltage (${{\bm{V}}_{{{\bf oc}}}}$), short-circuit current density (${{\bm{J}}_{{{\bf sc}}}}$), and output power, the latter under a wide range of irradiance conditions. The experimental procedure to detect the cracks relies on electroluminescence (EL) imaging, which is nondestructive and requires a relatively low amount of time. The Griddler software is adopted to translate the EL-taken image into${{\bm{V}}_{{{\bf oc}}}}$and${{\bm{J}}_{{{\bf sc}}}}$maps. The main findings can be summarized as follows: the nonuniformly and uniformly cracked cells are both jeopardized in terms of output power; the loss corresponding to the cell with nonuniform distribution of cracks is increasingly higher than the uniformly cracked counterpart as the irradiance hitting the cells grows; and all cells affected by nonuniform cracks are severely damaged in terms of fingers and rear busbar, which concur to limit the maximum output current.

This paper presents Si/SiGe:C and InP/GaAsSb HBTs which feature specific assets to address submillimeter-wave and THz applications. Process and modeling status and challenges are reviewed. The specific topics of thermal and substrate effects, reliability, and HF measurements are also discussed.