关键词: 扫描探针显微镜, 光电压, 电化学, 拉曼光谱, 氮化镓

Abstract: For further improvement of the performances of energy generation and storage devices, a better understanding of the mechanisms of carriers' excitation, transport and recombination in nanometer scale is essential, especially when there are plenty of surfaces, interfaces and defects involved in these kind of devices, which will influence carrier dynamics greatly. By combining scanning probe microscope (SPM) with confocal optical measurement system and electrochemical measurement system, a set of scanning near-field optics-electrical microscope (SNOEM) was developed. Local optical spectra and surface photovoltage/photocurrent can be acquired during scanning topographic images with a nanometer scale resolution. A special liquid cell was fabricated for the SPM interface evolution during electrochemical reactions at the interfaces between liquid and solid under light illumination. In this review, we introduce the main structure and functions of the instrument, together with its typical application in studying the electrical properties of graphene/GaN interfaces and the surface photovoltage properties of GaN surfaces. Graphene were found to be able to reduce the contact barrier with both P-doped GaN and N-doped GaN self-adaptively due to its unique linear energy band. Some wrinkles can even form local ohmic contacts. In the study of GaN photovoltage study, the thread dislocations introduced by a nanoindentation were observed as V-pits, where the photovoltage was lower than that on plane surface under ultra-violet illumination. By fitting the spatially resolved surface photovoltage spectroscopy curves, the hole diffusion length is 90 nm shorter and the surface electron recombination velocity is 1.6 times higher at an individual thread dislocation than those at plane surface. The results will be helpful in future device development.

Key words: scanning probe microscope, photovoltage, electrochemical, Raman spectroscopy, GaN