Introducing ultrafast EBIC: Spatially resolved transient analysis of an avalanche photodiode

We present ultrafast electron-beam-induced current (EBIC) measurements using an ultrafast scanning electron microscope (USEM) to investigate picosecond-scale transient behavior in semiconductor devices. This pump–probe technique enables spatially resolved observations of electric field dynamics at the micrometer to nanometer scale. We demonstrate this approach through a transient analysis of a dynamically biased avalanche photodiode (APD). Experimental results, supported by an equivalent circuit model, reveal that the gain dynamics under pulsed reverse bias are governed by the device's voltage-dependent capacitance. Furthermore, the radial dependence of the transient response highlights the ability of the method to resolve spatial variations in carrier dynamics. This technique offers insights into carrier transport, electric field distributions, and transient phenomena in a wide range of electronic and optoelectronic devices.