Cross sectional evaluation of boron doping and defect distribution in homoepitaxial diamond layers

Abstract

International audienceIn some diamond-based semiconducting devices, large variations of doping level are required over short distances. Tools to determine doping level and defects distribution should therefore be developed. The present contribution shows the capabilities of electron microscopy in this field. Focused ion beam (FIB-dual beam) cross section preparations allowed evaluating doping level in highly boron doped sample with doping transition down to some nm by diffraction contrast mode of transmission electron microscopy (CTEM) and by high angle annular dark field mode of scanning transmission electron microscopy (HAADF-STEM). The sensibility of the latter is around 1019cm-3 and, thus, cathodoluminescence (CL) is required for lower doping levels. Cross sectional analysis on FIB prepared lamella allowed to separate the epilayer behaviour from that of the substrate. Mid-gap centers involving boron, hydrogen and, for some peaks, also nitrogen are revealed. sp2 bonds are also present in the grown epilayer. These transitions make difficult the observation of excitonic recombinations in the cross section configuration

Stratigraphy of a diamond epitaxial three-dimensional overgrowth using doping superlattices

“…In order to study the intermediate stages of non-faceted or planarized overgrown diamond structures, a new approach is here proposed, which involves heavily doped nm-thick sublayers used as time markers in a stratigraphic 3 configuration, similar to previous studies of stacks of SiGe alloys 16 . As shown below for sample #2, the borondoped sublayers are easily distinguishable by transmission electron microscopy (TEM) in the conventional diffraction contrast mode 17 , and act as milestones of the growth plane orientation as growth proceeds. This method was designed to address both the issue of defect generation brought about by strong doping modulation, and that of progressive planarization of mesa or trench structures upon epitaxial overgrowth.…”

Three-Dimensional Diamond MPCVD Growth over MESA Structures: A Geometric Model for Growth Sector Configuration

“…Heavily doped nm-thick sublayers work as time markers in a such a stratigraphic configuration. Such layers, which are easily distinguishable by transmission electron microscopy in conventional diffraction mode (CTEM), act as milestones of the growth plane orientation as growth proceeds. , In this context, growth orientations are determined easily by measuring the misorientation of the doped layers with respect to the {100} orientation of the initial substrate surface.…”

Diamond for Electronics: Materials, Processing and Devices

“…This TEM related technique, however, is suitable to evaluate boron content when the dopant level is high, over the 10 19 cm −3 scale. When boron level is below that, CL on cross section foils constitutes a more suitable methodology [108]. By far, the control of defects, especially dislocations, in diamond is one of the main goals for diamond researchers, as they can be responsible for future leakage currents in the device.…”