Imaging of built-in electric field at a p-n junction by scanning transmission electron microscopy

Abstract

Precise measurement and characterization of electrostatic potential structures and the concomitant electric fields at nanodimensions are essential to understand and control the properties of modern materials and devices. However, directly observing and measuring such local electric field information is still a major challenge in microscopy. Here, differential phase contrast imaging in scanning transmission electron microscopy with segmented type detector is used to image a p-n junction in a GaAs compound semiconductor. Differential phase contrast imaging is able to both clearly visualize and quantify the projected, built-in electric field in the p-n junction. The technique is further shown capable of sensitively detecting the electric field variations due to dopant concentration steps within both p-type and n-type regions. Through live differential phase contrast imaging, this technique can potentially be used to image the electromagnetic field structure of new materials and devices even under working conditions.

Location and Visualization of Working p-n and/or n-p Junctions by XPS

“…In this case, the applied bias drops across the reversely biased n-p junction. Note that, although our ultimate lateral resolution of 30 μm does not permit direct investigation of the depletion zone of the junction itself, which is reported to be a few 10 nm145678910, its location and function can still be probed by XPS, as shown in Fig. 1(d).…”

Low magnification differential phase contrast imaging of electric fields in crystals with fine electron probes

“…In addition, for spatially varying long-range fields, within the phase object approximation the simple deflection model of Eq. (1) is only valid when the probe is much narrower than the scale over which the long-range field varies [18,29,30]. 2 However, low magnification imaging with a very fine probe means that the implied pixel size in the STEM images is much larger than the size of the probe.…”

“…Segmented detectors offer the ability to acquire STEM DPC maps in "live imaging", 4 i.e. at the fewsecond-long refresh rate of the scan during the experiment [18]. This gain comes at a price: segmented detectors only produce an approximation to the true CoM of the diffraction pattern, because the extent of the integrating detector segments means that information about the detailed electron intensity redistribution across each individual segment is lost.…”

“…STEM DPC has a long history of use in imaging magnetic field distributions within materials [1-3, 14, 15], but has had a recent resurgence through its application to imaging electric field structure, including the piezoelectric polarization fields in quantum wells [4,16], the ferroelectric polarization fields inside ceramics [17], the spontaneous polarization in semiconductor nanowires [5], and the built-in field within a p-n junction [18]. It has also been applied to imaging the electric fields of individual atomic columns [17,19,20].…”

Structure retrieval with fast electrons using segmented detectors

“…Such results can also be compared to those obtained using fixed-configuration segmented detectors. For example, Shibata et al [10][11][12][13] and Lazić et al [14] use fixed-configuration detectors for differential phase contrast imaging.…”