AbstractThe inner workings of semiconductor electronic and photonic devices, such as dopants, free charge carriers, electric potential, and electric field, are playing a crucial role in the function and performance of the devices. Electrical scanning probe microscopy (SPM) techniques have been developed and deployed to measure, with nanometric spatial resolution and high quantitative accuracy, the two-dimensional profiles of dopant, potential, electric field, and free carrier distribution, within unbiased and/or operating electronic and photonic devices. In this review paper, we summarize our latest SPM experimental results, including the scanning spreading resistance microscopy and scanning capacitance microscopy of terahertz quantum cascade lasers, scanning capacitance microscopy of non-volatile memory devices, scanning voltage microscopy of terahertz quantum cascade lasers, and scanning voltage microscopy of interband cascade lasers. Interpretation of the measured quantities are presented and calibrated, demonstrating that important internal physical quantities and inner mechanisms of device operation can be uncovered. It reveals that the novel SPM techniques would find more applications to the emerging semiconductor quantum devices and nanoelectronics.