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Underlying physics has been put forward and an experimental verification given for in situ determination of deformation potentials in Si-doped GaAs through a quantitative assessment of micro-/nanoscopic surface stress fields. Highly localized spectroscopic stress assessments could be achieved using a field emission scanning electron microscope as an energy source for stimulating cathodoluminescence emission from a Si-doped GaAs wafer. The deformation potentials were obtained from the local (elastic) residual strain fields stored in the neighborhood of an indentation print. The three independent GaAs deformation potentials could be obtained from a single measurement set and from mixed strain fields including tensile and compressive strains, while all the previously published characterizations were made in compression and on different samples. For these reasons, the deformation potentials determined in this study may prove more reliable and valid in a wider strain range as compared to those from previously published study. The proposed experimental method is suitable for in situ assessments of epitaxially grown thin-film materials and other zinc-blende-like III-V semiconductor heterostructures and alloys. [ABSTRACT FROM AUTHOR]

A spatially resolved cathodoluminescence piezospectroscopic analysis is attempted for the high-resolution evaluation of the stress field developed ahead of the tip of an equilibrium crack propagating in a semiconductor. GaN was selected for this assessment as a paradigm semiconductor material. Quantitative measurements of in-plane luminescence probe response function (PRF) were preliminarily performed at different acceleration voltages upon scanning across a straight and atomically sharp interface between GaN and gold metal. Then, based on the knowledge of PRF, the convoluting effect due to the finite size of the electron probe could be corrected and an improved plot of the crack-tip stress field could be retrieved by a computer-aided data restoration procedure. The crack-tip stress intensity factor KI obtained by the cathodoluminescence piezospectroscopic method was compared with that obtained on the same crack path according to high-resolution measurements of crack-tip opening displacement. This study not only shows that a nanometer-scale spatial resolution can be experimentally achieved in a stress analysis of semiconductor materials but also that a stress data treatment based on experimental PRF is a viable approach to greatly reduce the error involved with the finite size of the electron probe. [ABSTRACT FROM AUTHOR]

A piezospectroscopic (PS) cathodoluminescence (CL) study has been carried out on a Cu-Ta/SiOx (carbon-doped) model chip prepared on a Si substrate. The PS approach was applied to CL spectra arising from optically active point defects in dielectric silica. The red CL emission arising from nonbridging oxygen hole centers (NBOHC) in the carbon-doped SiOx dielectric layer was calibrated and used as a stress sensor. This approach enabled us to locate the trace of the residual stress tensor, as locally developed during manufacturing process in the dielectric interlayers between Cu-Ta interconnects. A minimally invasive electron beam allowed probing local residual stress fields with an improved spatial resolution as compared to more conventional photostimulated PS techniques applied to the Si substrate. In addition, a two-dimensional deconvolution procedure was attempted to retrieve the “true” residual stress distribution piled up between adjacent Cu-Ta lines, according to a theoretical model for embedded structural elements. As probed on the nanometer scale by the NBOHC sensor, the interfaces were found under a substantially enhanced residual stress, characteristic for low-temperature Si/SiOx growth in the presence of metallic interconnects. CL/PS spectroscopy represents an improved tool to quantitatively monitor the residual stresses developed at SiOx/metal interfaces, thus opening the possibility to systematically engineer the interface itself in search for high-reliability Si-based devices. [ABSTRACT FROM AUTHOR]

The stress dependence of the room-temperature cathodoluminescence spectrum of N-doped cubic silicon carbide has been evaluated in a field-emission-gun scanning electron microscope, using the electron beam as an excitation source for luminescence emission. The electron-stimulated spectrum was dominated by only one broad band centered at about 544 nm, with a broad shoulder centered at a slightly lower energy level (≈572 nm). The cathodoluminescence spectrum, which was attributed to the four-particle N-bound excitonic transition, arose from substitutional N in the cubic silicon carbide lattice. Using experimentally measured probe response functions and energy shift magnitude collected near the tip of a Vickers indentation microcrack, it was possible to retrieve the actual magnitude of the piezospectroscopic coefficient [i.e., the slope of a linear plot of spectral band shift versus the trace of the stress tensor: Π=0.61±0.02 nm/GPa] of the N-bound exciton (cumulative) band of cubic silicon carbide. [ABSTRACT FROM AUTHOR]

A microscopic procedure has been proposed for evaluating the stress dependence of the (room-temperature) cathodoluminescence (CL) excitonic band emitted from the (0001) crystallographic plane of GaN in a field-emission-gun scanning electron microscope. The room-temperature near-band-gap emission (generally referred to as the excitonic band) mainly consisted of a band arising from free exciton (FX). However, an asymmetric morphology was found for the band, which thus needed to be deconvoluted into the main FX band and a shoulder. The spectral location at intensity maximum of the overall excitonic band under stress-free conditions was observed at room temperature at around 365 nm. Experimentally measured spectral shifts were precisely retrieved nearby the tip of a Vickers indentation microcrack, while CL intensity probe response functions were collected at different acceleration voltages at a sharp interface between a GaN film and its sapphire substrate. Based on these assessments, the magnitude of the piezospectroscopic coefficient (i.e., the spectral shift rate versus the trace of a biaxial stress tensor) Π=1.35±0.01 nm/GPa of the excitonic (cumulative) band of GaN could be evaluated. This study not only emphasizes the importance of microscopic piezospectroscopic calibration procedures for precise residual stress assessments in GaN-based devices, but also the need of deconvoluting the electron probe for minimizing the error involved with its finite size. [ABSTRACT FROM AUTHOR]