Role of subsurface defects in metal-ZnO(0001¯) Schottky barrier formation

Mosbacker, H. L.; Hage, S. El; González, M.; Ringel, S. A.; Hetzer, Michael; Look, David C.; Cantwell, G.; Zhang, J.; Song, Jae Hee; Brillson, L. J.

doi:10.1116/1.2756543

Cited by 30 publications

(17 citation statements)

References 21 publications

(12 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…8 show that the present ZnO samples belong to the "low-defect" category, as discussed in Ref. 28. Interestingly, we find significant changes in the deep level versus nearband-edge ͑NBE͒ emission intensities as a function of incident electron beam energy ͑E b = 3-8 keV͒ for the Pd-SBDs but not for the Au-SBDs, consistent with the DLTS results.…”

Section: Resultssupporting

confidence: 90%

“…10,28 This type of experiment is especially powerful in conjunction with I-V analysis and can help determine the most desirable combinations of substrate, metal, and surface treatment. The main conclusions of these studies are that ͑i͒ native point defects are present at and below the ZnO surface and strongly influence the diode rectification ratio and ideality factor, ͑ii͒ the magnitudes of the usual deep levels at 2.1, 2.5, or 3.0 eV, as measured by DRCLS, can vary by orders of magnitude depending on substrate growth technique, surface processing, and metallization, and ͑iii͒ some metals, such as Al, can induce chemical interactions with ZnO, resulting in the formation of subsurface defects.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Surface traps in vapor-phase-grown bulk ZnO studied by deep level transient spectroscopy

Fang

Claflin

Dong

et al. 2008

Journal of Applied Physics

Self Cite

View full text Add to dashboard Cite

Deep level transient spectroscopy, current-voltage, and capacitance-voltage measurements are used to study interface traps in metal-on-bulk-ZnO Schottky barrier diodes ͑SBDs͒. c-axis-oriented ZnO samples were cut from two different vapor-phase-grown crystals, and Au-and Pd-SBDs were formed on their ͑0001͒ surfaces after remote oxygen-plasma treatment. As compared to Au-SBDs, the Pd-SBDs demonstrated higher reverse-bias leakage current and forward-bias current evidently due to higher carrier concentrations, which might have been caused by hydrogen in-diffusion through the thin Pd metal. The dominant traps included the well-known bulk traps E 3 ͑0.27 eV͒ and E 4 ͑0.49 eV͒. In addition, a surface-related trap, E s ͑0.49 eV͒, is observed but only in the Pd-SBDs, not in the Au-SBDs. Trap E s is located at depths less than about 95 nm and shows an electron capture behavior indicative of extended defects. A possible correspondence between trap E s and the well-known 2.45 eV green band is suggested by depth-resolved cathodoluminescence spectroscopy on the same samples, which reveals an increase in the intensity of this band within ϳ100 nm of the Pd/ZnO interface.

show abstract

Section: Resultssupporting

confidence: 90%

Section: Resultsmentioning

confidence: 99%

Surface traps in vapor-phase-grown bulk ZnO studied by deep level transient spectroscopy

Fang

Claflin

Dong

et al. 2008

Journal of Applied Physics

Self Cite

View full text Add to dashboard Cite

show abstract

“…Similar differences are evident for Pd and Pt which, as with Au, alloy with Zn at elevated temperature, versus Al and Ir, which, as with Ta, form oxides. 15 Thus the increased 2.1 ͑2.5͒ eV emissions for Au ͑Ta͒ can be associated with Zn ͑O͒-deficient defects near the metal interface. Furthermore, Figs.…”

mentioning

confidence: 99%

Thermally driven defect formation and blocking layers at metal-ZnO interfaces

Mosbacker

Zgrabik

Hetzer

et al. 2007

Applied Physics Letters

Self Cite

View full text Add to dashboard Cite

The authors used depth-resolved cathodoluminescence spectroscopy and current-voltage measurements to probe the temperature-dependent formation of native point defects and reaction layers at metal-ZnO interfaces and their effect on transport properties. These results identify characteristic defect emissions corresponding to metal-Zn alloy versus oxide formation. Au alloys with Zn above its eutectic temperature, while Ta forms oxide blocking layers that reduce current by orders of magnitude at intermediate temperatures. Defects generated at higher temperatures and/or with higher initial defect densities for all interfaces produce Ohmic contacts. These reactions and defect formation with annealing reveal a thermodynamic control of blocking versus Ohmic contacts.

show abstract

“…DLOS and deep level transient spectroscopy (DLTS) measurements exhibit energy level transitions that correspond to the DRCLS features under bias conditions that probe comparable depths. 46 At Pd-ZnO(0001) contacts with relatively low native point defect emissions, DRCL spectra exhibit a midgap defect emission at 2.45 eV that grows more than twofold with decreasing excitation depth in the <20-100 nm range. 1/C 2 -V net carrier concentrations exhibit a corresponding increase by >2-5 Â from the bulk to $70-80 nm.…”

Section: à3mentioning

confidence: 99%

Interplay of native point defects with ZnO Schottky barriers and doping

Brillson¹,

Dong²,

Tuomisto³

et al. 2012

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

View full text Add to dashboard Cite

A combination of depth-resolved electronic and structural techniques reveals that native point defects can play a major role in ZnO Schottky barrier formation and charged carrier doping. Previous work ignored these lattice defects at metal-ZnO interfaces due to relatively low point defect densities in the bulk. At higher densities, however, they may account for the wide range of Schottky barrier results in the literature. Similarly, efforts to control doping type and density usually treat native defects as passive, compensating donors or acceptors. Recent advances provide a deeper understanding of the interplay between native point defects and electronic properties at ZnO surfaces, interfaces, and epitaxial films. Key to ZnO Schottky barrier formation is a massive redistribution of native point defects near its surfaces and interfaces. It is now possible to measure the energies, densities, and in many cases the type of point defects below the semiconductor-free surface and its metal interface with nanoscale precision. Depth-resolved cathodoluminescence spectroscopy of deep level emissions calibrated with electrical techniques show that native point defects can (1) increase by orders of magnitude in densities within tens of nanometers of the semiconductor surface, (2) alter free carrier concentrations and band profiles within the surface space charge region, (3) dominate Schottky barrier formation for metal contacts to ZnO, and (4) play an active role in semiconductor doping. The authors address these issues by clearly identifying transition energies of leading native point defects and defect complexes in ZnO and the effects of different annealing methods on their spatial distributions on a nanoscale. These results reveal the interplay between ZnO electronic defects, dopants, polarity, and surface nanostructure, highlighting new ways to control ZnO Schottky barriers and doping.

show abstract

Role of subsurface defects in metal-ZnO(0001¯) Schottky barrier formation

Cited by 30 publications

References 21 publications

Surface traps in vapor-phase-grown bulk ZnO studied by deep level transient spectroscopy

Surface traps in vapor-phase-grown bulk ZnO studied by deep level transient spectroscopy

Thermally driven defect formation and blocking layers at metal-ZnO interfaces

Interplay of native point defects with ZnO Schottky barriers and doping

Contact Info

Product

Resources

About