Electrical Scanning Probe Microscopy: Investigating the Inner Workings of Electronic and Optoelectronic Devices

Semiconductor electronic and optoelectronic devices such as transistors, lasers,modulators, and detectors are critical to the contemporary computing and communications infrastructure. These devices have been optimized for efficiency in power consumption and speed of response. There are gaps in the detailed understanding of the internal operation of these devices. Experimental electrical and optical methods have allowed comprehensive elaboration of input–output charac-teristics, but do not give spatially resolved information about currents, carriers, and potentials on the nanometer scale relevant to quantum heterostructure device operation. In response, electrical scanning probe techniques have been developed and deployed to observe experimen-tally, with nanometric spatial resolution, two-dimensional profiles of the electrical resistance, capacitance, potential, and free carrier distribution, within actively driven devices. Experimen-tal configurations for the most prevalent electrical probing techniques based on atomic force microscopy are illustrated with considerations for practical implementation. Interpretation of the measured quantities are presented and calibrated, demonstrating that internal quantities of device operation can be uncovered. Several application areas are examined: spreading resis-tance and capacitance characterization of free carriers in III-V device structures; acquisition of