Characterization of deep levels in zinc oxide

Simpson, Jean; Cordaro, J. F.

doi:10.1063/1.339919

Cited by 176 publications

(98 citation statements)

References 12 publications

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“…4 Various growth conditions also can influence the presence of midgap impurities and point defects and such deep centers can produce undesired trapping and carrier recombination. In past years, deep level transient spectroscopy ͑DLTS͒ has been used to study traps ͑mainly electron traps͒ in n-type bulk ZnO grown by the hydrothermal, 5 vapor-phase, 6 and pressurized melt growth 7 methods. In most of these cases, the DLTS test structures were Schottky-barrier diodes.…”

Section: Introductionmentioning

confidence: 99%

Electron and hole traps in N-doped ZnO grown on p-type Si by metalorganic chemical vapor deposition

Fang

Claflin

Kerr

et al. 2007

Journal of Applied Physics

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Electron and hole traps in N-doped ZnO were investigated using a structure of n + -ZnO:Al/ i-ZnO/ ZnO:N grown on a p-Si substrate by metalorganic chemical vapor deposition ͑for growth of the ZnO:N layer͒ and sputtering deposition ͑for growth of the i-ZnO and n + -ZnO:Al layers͒. Current-voltage and capacitance-voltage characteristics measured at temperatures from 200 to 400 K show that the structure is an abrupt n + − p diode with very low leakage currents. By using deep level transient spectroscopy, two hole traps, H3 ͑0.35 eV͒ and H4 ͑0.48 eV͒, are found in the p-Si substrate, while one electron trap E3 ͑0.29 eV͒ and one hole trap H5 ͑0.9 eV͒ are observed in the thin ZnO:N layer. Similarities to traps reported in the literature are discussed.

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Section: Introductionmentioning

confidence: 99%

Electron and hole traps in N-doped ZnO grown on p-type Si by metalorganic chemical vapor deposition

Fang

Claflin

Kerr

et al. 2007

Journal of Applied Physics

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“…Since the number of shallow donors introduced by radiation will balance the number of radiation induced acceptors, we will not observe any drastic change in the free carrier concentration and neither will we detect any major DLTS peaks in the temperature domain investigated. This possibility will have to be verified by performing admittance spectroscopy measurements 12 to facilitate the detection of defect levels too deep to be detected by DLTS, and Hall and photoluminescence measurements to detect the shallow donors ͑too shallow to be detected by DLTS͒. At this point, it should be noted that Look et al have reported an increase in concentration of one of the shallow donors in ZnO after electron irradiation.…”

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confidence: 99%

Electrical characterization of 1.8 MeV proton-bombarded ZnO

Auret

Goodman

Hayes

et al. 2001

Applied Physics Letters

303

177

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We report on the electrical characterization of single-crystal ZnO and Au Schottky contacts formed thereon before and after bombarding them with 1.8 MeV protons. From capacitance–voltage measurements, we found that ZnO is remarkably resistant to high-energy proton bombardment and that each incident proton removes about two orders of magnitude less carriers than in GaN. Deep level transient spectroscopy indicates a similar effect: the two electron traps detected are introduced in extremely low rates. One possible interpretation of these results is that the primary radiation-induced defects in ZnO may be unstable at room temperature and anneal out without leaving harmful defects that are responsible for carrier compensation.

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“…Common to the majority of these reports for poly-or singlecrystalline ZnO, is the presence of a defect, L2, with a level situated around 0.3 eV below the conduction band. [8][9][10][11][12][13][14] In addition, single-crystal ZnO grown by the hydrothermal technique contains a defect with a level estimated at E C Ϫ0.34 eV, from temperature-dependent Hall-effect measurements; 1 this defect is probably related to L2. Another defect, L1, with a level reported between 0.18 and 0.23 eV, 8,10,12,13 has only been observed in poly-ZnO, but little is known about its identity.…”

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confidence: 99%

Electrical characterization of vapor-phase-grown single-crystal ZnO

Auret

Goodman

Legodi

et al. 2002

Applied Physics Letters

172

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Gold Schottky-barrier diodes ͑SBDs͒ were fabricated on vapor-phase-grown single-crystal ZnO. Deep-level transient spectroscopy, using these SBDs, revealed the presence of four electron traps, the major two having levels at 0.12 eV and 0.57 below the conduction band. Comparison with temperature-dependent Hall measurements suggests that the 0.12 eV level has a temperature activated capture cross section with a capture barrier of about 0.06 eV and that it may significantly contribute to the free-carrier density. Based on the concentrations of defects other than this shallow donor, we conclude that the quality of the vapor-phase-grown ZnO studied here supercedes that of other single-crystal ZnO reported up to now. © 2002 American Institute of Physics. ͓DOI: 10.1063/1.1452781͔During the past few decades, ZnO has been used in many, diverse products. Its applications, among others, include phosphors, piezoelectric transducers, varistors, alcohol synthesis catalysis, and gas sensing. In a recent review, however, where the properties of ZnO are summarized, 1 it was pointed out that ZnO can be used for several other, more advanced, electro-optical applications. Based on the fact that ZnO has a direct bandgap of 3.4 eV, it is expected to fulfill a similar role as GaN in optoelectronics, i.e., play an important role in realizing blue and ultraviolet light-emitting diodes and lasers, as well as daylight-blind UV detectors. Similar to that of GaN, its large band gap renders ZnO suitable for the fabrication of high-temperature, high-power devices with application, among others, in space where typical operating temperatures exceed 200°C. High-quality single-crystal ZnO can be successfully grown in bulk. 2 A very important consequence of this is that owing to the relatively close match in lattice constants, single-crystal ZnO may be used as a substrate to grow epitaxial GaN that is well oriented with respect to the substrate and that has a reduced defect density. 3 Further practical advantages of ZnO include amenability to conventional wet chemistry etching, which is compatible with Si technology 4 ͑unlike the case for GaN͒.An important issue in ZnO technology is establishing a technology for the fabrication of high-quality Schottkybarrier diodes ͑SBDs͒. SBDs are of key importance to probe defects in semiconductors by junction spectroscopic characterization techniques, such as deep-level transient spectroscopy ͑DLTS͒ ͑Ref. 5͒ and admittance spectroscopy ͑AS͒. 6 They are also important structures for metal-semiconductor field-effect transistors ͑MESFETs͒ and detectors. A limited amount of research regarding Schottky contacts to ZnO was carried out in the 1960s, where among other things the barrier height of some metal contacts to vacuum-cleaved ZnO was reported. 7 However, up to now, no systematic studies of surface characterization as a function of cleaning method have been performed; i.e., the influence of different cleaning methods on the surface quality of ZnO and the quality of Schottky contacts to ZnO have not been compared...

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Characterization of deep levels in zinc oxide

Cited by 176 publications

References 12 publications

Electron and hole traps in N-doped ZnO grown on p-type Si by metalorganic chemical vapor deposition

Electron and hole traps in N-doped ZnO grown on p-type Si by metalorganic chemical vapor deposition

Electrical characterization of 1.8 MeV proton-bombarded ZnO

Electrical characterization of vapor-phase-grown single-crystal ZnO

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