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Trap levels in the atomic layer deposition-ZnO/GaN heterojunction—Thermal admittance spectroscopy studies
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10.1063/1.4805655
/content/aip/journal/jap/113/19/10.1063/1.4805655
http://aip.metastore.ingenta.com/content/aip/journal/jap/113/19/10.1063/1.4805655

Figures

Image of FIG. 1.
FIG. 1.

The characteristics of the discussed junction measured at RT with different voltage frequency together with the equivalent circuit (see the inset). Observed capacitance drop is approximately Δ  = 1 nF within the tested range of reverse bias.

Image of FIG. 2.
FIG. 2.

The characteristics of the discussed junction measured at RT, presented in linear (a) and semi-logarithmic (b) scale. The series resistance appears to be about 250 Ω. The inset in Fig. 2(a) shows the narrow range of applied bias (±0.5 V) in which the structure reveals pure rectifying behavior.

Image of FIG. 3.
FIG. 3.

The Mott-Schottky analysis of the ZnO/GaN heterostructure producing the donor concentration in ZnO and diode's built-in voltage (see the dotted linear fit). Low frequency ( = 10 kHz) measurements are required (the black solid line) as the high frequency regime ( = 1 MHz) yields the strong and meaningless () dependence (shown by the black dashed line).

Image of FIG. 4.
FIG. 4.

The admittance spectroscopy data (capacitance () and loss ()) of the ZnO/GaN heterostructure obtained between 140 K (thick blue dashed curves) and 300 K (thick red solid curves)—as indicated.

Image of FIG. 5.
FIG. 5.

Admittance spectrum of the capacitance () and loss () of ZnO/GaN heterostructure as a function of applied bias in the range of −0.48 V (green curves, dashed one for and solid one for ) up to +0.2 V (red curves, dashed one for and solid one for ). The results were obtained at RT.

Image of FIG. 6.
FIG. 6.

Capacitance transients measured between 230 K and room temperature (as indicated). To determine the capacitance relaxation time either single or double exponential decay formula—see Eq. (3) —was fitted. This yielded the trap energy of about 0.57 eV. The applied bias was:  = 0 V and  = −2 V.

Image of FIG. 7.
FIG. 7.

The Arrhenius plot of the ZnO/GaN heterojunction with the linear fits estimating the donors' activation (trap) energies . The applied bias was:  = 0 V and  = −2 V. The measurements were performed within 300 s using 10 kHz signal of the voltage.

Tables

Generic image for table
Table I.

The estimated capacitance relaxation times (s) and emission rates (s) at indicated temperatures for ZnO/GaN heterostructure tested for 300 s using bias conditions of  = 0 V and  = −2 V. Only the transient obtained at  = 230 K was collected for a longer time (400 s). In case of fitting with the double-exponential formula only the meaningful value of was considered—see description in the text. Basing on these data, a defect level with the energy of ≈ (0.57 ± 0.03) eV was found.

Generic image for table
Table II.

Calculated activation energy, trap density and capture cross-section for defect levels found in the examined ZnO/GaN heterostructure.

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/content/aip/journal/jap/113/19/10.1063/1.4805655
2013-05-17
2014-04-20
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Trap levels in the atomic layer deposition-ZnO/GaN heterojunction—Thermal admittance spectroscopy studies
http://aip.metastore.ingenta.com/content/aip/journal/jap/113/19/10.1063/1.4805655
10.1063/1.4805655
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