SEM techniques for characterization of GaN nanostructures and devices

Abstract

The scanning electron microscope (SEM) techniques play a key role in the characterization of various inorganic and/or organic semiconducting materials, micro-/nanostructures and devices. The power of the SEM methods is mainly in imaging, characterization and diagnostics of local near surface properties. Among a variety of the SEM methods, Cathodoluminescence (CL) and Electron Beam Induced Current (EBIC) methods have been extensively used for characterization of generation/recombination phenomena and electrical properties of bulk semiconductors and semiconductor structures [1]. Exploitation of these methods allow to visualize the electrically active defects such as dislocations, grain boundaries and inhomogeneities and to estimate the diffusion length, lifetime and surface recombination velocity of minority carriers. In addition, EBIC can be used for investigation and diagnostics of SCR of Schottky and p-n junctions, which extends its applications, in combination with other techniques such as Voltage Contrast (VC), to functional diagnostics of electronic devices biased at operation point. Currently, various modifications and improvements of “standard” SEM methods are developed to improve their resolution and sensitivity for investigations of advanced structures and devices structural, optical and electrical properties. Various sample preparation and micromanipulation / microprobe techniques are examined to localize appropriate signals with the aim to improve the spatial resolution while for extreme depth resolution low acceleration voltages of SEM techniques are utilized [2]. In addition, complex signal acquisition and processing techniques are implemented to achieve time and frequency resolution and to gain required information about the sample properties.