Self-compensation, the tendency of a crystal to lower its energy by forming point defects to counter the effects of a dopant, is here quantitatively proven. Based on a new theoretical formalism and several different experimental techniques we demonstrate that the addition of 1.4 x 10 21 -cm -3 Ga donors in ZnO causes the lattice to form 1.7 x 10 20 -cm -3 Zn-vacancy acceptors. The calculated V Zn formation energy of 0.2 eV is consistent with predictions from density functional theory. Our formalism is of general validity and can be used to investigate self-compensation in any degenerate semiconductor material.2

Depth-resolved cathodoluminescence spectroscopy ͑DRCLS͒ reveals the evolution of surface and near surface defects at polar surfaces with remote oxygen plasma ͑ROP͒ treatment. Furthermore, this evolution exhibits significant differences that depend on surface polarity. ROP decreased the predominant 2.5 eV defect emission related to oxygen vacancies on the O face, while creating a new 2.1 eV defect emission on the Zn face that increases with ROP time. The surface-located 2.1 eV emission correlates with carrier profiles from capacitance-voltage measurements and a shift of the E3 trap to higher binding energy from deep level transient spectroscopy ͑DLTS͒. This result suggests that ROP generates Zn vacancies on the Zn face which act as compensating acceptors at the surface and in the near surface region. Secondary ion mass spectrometry ͑SIMS͒ shows no polarity dependence due to impurities. We conclude that the near-surface deep level optical emissions and free carrier densities of ZnO depend strongly on the ROP modulation of native defects related to Zn or O vacancies.

We used depth-resolved microcathodoluminescence spectroscopy (DRCLS) and Kelvin probe force microscopy (KPFM) to measure and map the temperature distribution and defect generation inside state-of-the-art AlGaN/GaN-based high electron mobility transistors (HEMTs) on a scale of tens of nanometers during device operation. DRCLS measurements of near band edge energies across the HEMT’s source-gate-drain regions reveal monotonic temperature increases across the submicron gate-drain channel, peaking under the drain side of the gate. DRCLS defect emissions mapped laterally and localized depthwise near the two-dimensional electron gas interface increase with device operation under the drain-side gate and correlate with higher KPFM surface potential maps.

The impact of electronically‐active native point defects on ZnO optoelectronic technologies at the nanoscale is only now being explored. We are able to address the impact of these defects on Schottky barrier formation and doping using a combination of depth‐resolved and scanned probe techniques. We clearly identify the optical transitions and energies of VZn and VZn clusters, Ga on Zn site donors, Li on Zn sites, the effects of different annealing methods on their spatial distributions in ion‐implanted as well as Ga grown‐in ZnO, and how VZn, VZn clusters, and VO complexes contribute to near‐ and sub‐surface carrier density. These results reveal the interplay between ZnO electronic defects, polarity, and surface nanostructure. Overall, the influence of native point defects on doping, Schottky barriers, and transport point to new ways for controlling these properties (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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