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

Abstract

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 characteristics, 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 experimentally, with nanometric spatial resolution, two-dimensional profiles of the electrical resistance, capacitance, potential, and free carrier distribution, within actively driven devices. Experimental 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 resistance and capacitance characterization of free carriers in III-V device structures; acquisition of electric potential and field distributions of semiconductor lasers, nanocrystals, and thin films; scanning voltage analysis on diode lasers-the direct observation of the internal manifestations of current blocking breakdown in a buried heterostructure laser, the effect of current spreading inside actively biased ridge waveguide lasers, anomalously high series resistance encountered in ridge lasers-as well as in CMOS transistors; and free-carrier measurement of working lasers with scanning differential spreading techniques. Applications to emerging fields of nanotechnology and nanoelectronics are suggested.

Probing Local Surface Potential of Quasi‐One‐Dimensional Systems: A KPFM Study of P3HT Nanofibers

“…The parameters L and LH amount to 20 nm and 10 nm, respectively, yielding a theoretical value of 5.1 for the ratio obtained by the Equation 6. This value is in good agreement with the measured one of (5.6 AE 0.9) obtained from the deconvolution procedure.…”

“…It is therefore most important to quantitatively map simultaneously the morphology and the electronic properties of quasi-one-dimensional systems with a high degree of precision. [6] Kelvin Probe Force Microscopy (KPFM) [7] makes it possible to obtain a quantitative measurement of the surface potential (SP) [8,9] of isolated nanostructures both in air and in vacuum environments with a nanoscale resolution. Moreover it provides quantitative insight into other electronic properties of the investigated architecture including the work function, band bending and electrical polarization.…”

Field-effect-tuned lateral organic diodes

“…The comparison of the surface potential measured by SKPM on each side of the junction gives (at ∼100-nm lateral resolution) the chemical potential difference (CPD) on the two sides of the junction, which equals the local vacuum level shift at the heterojunction [caused by band bending or an interface dipole (28)]. Both SKPM and electric force microscopy (EFM) have been widely used to investigate the physics of inorganic semiconductor devices (29) , organic semiconductor devices (24,26,(30)(31)(32)(33)(34)(35)(36), and ionic devices (37)(38)(39). The lateral geometry of our diodes gives us easy access to the active interface, allowing us to use SKPM to characterize the interfacial CPD as a function of injected charge.…”

Kelvin force microscopy on a (Al 1-x Ga x ) 0.5 In 0.5 P light-emitting diode

“…It offers a spatial resolution of several nanometers 3 . Voltage drop measurements at single quantum wells has been demonstrated e. g. in a multiquantum-well ridge-waveguide InGaAsP/InP laser 7,8 .…”