Hexagonal-based pyramid void defects in GaN and InGaN

Abstract

We report a void defect in gallium nitride (GaN) and InGaN, revealed by aberration-corrected scanning transmission electron microscopy (STEM). The voids are pyramids with symmetric hexagonal f0001g base facets and f10 11g side facets. Each pyramid void has a dislocation at the peak of the pyramid, which continues up along the ½0001 growth direction to the surface. Some of the dislocations are hexagonal open core screw dislocations with f10 10g side facets, varying lateral widths, and varying degrees of hexagonal symmetry. STEM electron energy loss spectroscopy spectrum imaging showed a large C concentration inside the void and on the void surfaces. There is also a larger C concentration in the GaN (or InGaN) below the void than above the void. We propose that inadvertent carbon deposition during metal organic chemical vapor deposition growth acts as a mask, stopping the GaN deposition locally, which in combination with lateral overgrowth, creates a void. Subsequent layers of GaN deposited around the C covered region create the overhanging f10 11g facets, and the meeting of the six f10 11g facets at the pyramid's peak is not perfect, resulting in a dislocation. V

Impurity distribution and microstructure of Ga-doped ZnO films grown by molecular beam epitaxy

“…Our previous investigations compare the grain size derived from XRD and STEM to the electron mobility. 14,16 There are sufficiently good correlations with grain size from STEM data and XRD data in the whole range of grain boundary sizes to show a significant contribution of grain-boundary scattering for our samples. 16 Careful analysis of the electrical data reveals a significant effect of ionized impurities and polar optical phonon scattering, especially for samples with large grains and thus relatively high carrier mobility.…”

“…14,16 There are sufficiently good correlations with grain size from STEM data and XRD data in the whole range of grain boundary sizes to show a significant contribution of grain-boundary scattering for our samples. 16 Careful analysis of the electrical data reveals a significant effect of ionized impurities and polar optical phonon scattering, especially for samples with large grains and thus relatively high carrier mobility. 14 However, the formation of numerous voids and IDBs in GZO films grown on a-sapphire under metal-rich conditions means that electron mobilities could be limited by scattering at other extended defects as well.…”

“…16 We are confident that carbon microanalysis reflects the state of the sample and not the accumulation of carbon due to the microscope vacuum.…”

“…The plasma power was 400 W and Zn cell temperature was 350 C for all the layers. The substrate temperature T sub of all samples characterized in this study was 400 C, the Ga cell temperature T Ga , which controls the Ga flux, was 600 C. The effects of varying the substrate temperature 14,15 and the Ga cell temperature 16 on electrical and structural characteristics were published elsewhere. The flux of reactive oxygen was varied.…”

Deep-level defects related to the emissive pits in thick InGaN films on GaN template and bulk substrates

“…The decreased contents of In, Ga, and N inside the pits may be caused by the accumulated C working as a mask. 19 We ruled out unintentional adsorption of C impurities during the measurements because of our careful experimental procedure. The average impurity levels of C, O, and H in the InGaN films and GaN interlayers were lower than the detection limit of secondary-ion mass spectrometry.…”