Quantitative Assessment of Crack-Tip Stress Field in Semiconductor GaN Using Electrostimulated Piezo-Spectroscopy

The piezo-spectroscopic (PS) effect, which may be defined as the shift in wavelength of a spectroscopic transition in a solid in response to an applied strain or stress, may occur both in crystalline and in amorphous structures, regardless of the particular spectroscopic transition involved (e.g., luminescence or Raman spectrum), and independent of the specific mechanism of luminescence emission (i.e., including spectra generated from substitutional impurities, optically active point defects, etc.). The PS effect can be monitored on electro-stimulated spectra when the scale on which the needed characterization lie is of a nanometer length. This effect, being a physical property of the studied material, should be calibrated case by case. The high scanning speed (and computer control) of the electron beam, which can be easily obtained with scan coils, is unsurpassed. Since the most recently developed optoelectronic devices have active areas of submicron dimensions and many of them less than 100 nm, no obvious choice is left but urgently developing an electro-stimulated probe for nano-scale residual stress assessments. In this paper, we show the feasibility of nano-scale stress assessments in the neighborhood of the tip of a crack propagating in GaN, selected as a paradigm semiconductor material.