Mina Jung

High-Quality p-Type ZnO Films Grown by Co-Doping of N and Te on Zn-Face ZnO Substrates

This article will report the epitaxial growth of high-quality p-type ZnO layers on Zn-face ZnO substrates by nitrogen and tellurium (N+Te) co-doping. ZnO:[N+Te] films show p-type conductivity with a hole concentration of 4×1016 cm-3, while ZnO:N shows n-type conduction. The photoluminescence of ZnO:N shows broad bound exciton emission lines. Meanwhile, ZnO:[N+Te] layers show dominant A0X emission line at 3.359 eV, with a linewidth as narrow as 1.2 meV. Its X-ray linewidth shows narrower line width of 30 arcsec. Detailed investigation of photoluminescence properties of (N+Te) codoped ZnO layers suggest that the binding energy of N acceptors lies in a range of 121–157 meV.

Influence of growth mode on the structural, optical, and electrical properties of In-doped ZnO nanorods

The growth mechanism of In-doped ZnO (ZnO:In) nanorods grown on AuGe/Si(111) substrates has been investigated. Unlike to general vapor-liquid-solid mechanism, the adatom kinetics on the surface determines the length-diameter relationship [L(D)], initial nuclei size (D∗), and spatial distribution of impurity atoms. The incorporated In-concentration was estimated to be within solid solubility limit of ZnO in terms of x-ray diffraction analysis, but the evolution of photoluminescence peak position and intensity revealed an evidence of extrinsic carrier increment. Hall-effect measurement was used to evaluate the carrier concentration of ZnO:In nanorods.

Correlation between structural and optical properties of a-plane GaN films grown on r-plane sapphire by metal organic chemical-vapor deposition

The authors have studied the photoluminescence (PL) intensities of a-plane (11-20) GaN films (a-GaN) as a function of x-ray rocking-curve (XRC) linewidth values measured in both c- and m-axis directions. PL intensity of well-known luminescence lines such as 3.47 eV (bound exciton emission), 3.41 eV (basal-plane stacking fault related emission), and 3.29 eV (defect induced emission) are discussed in terms of XRC linewidth values. PL intensities reveal a close relationship with XRC linewidth measured in the c-axis direction, while an unusual relationship was observed between PL intensity and XRC linewidth in the m-axis direction. Inhomogeneous strain along the m-axis direction of a-GaN film is discussed as a cause of XRC linewidth broadening, rather than the formation of structural defects.

Fabrication of one-dimensional and two-dimensional periodically polarity inverted ZnO structures using the patterned CrN buffer layers

By employing the simple patterning and regrowth procedures, one-dimensional and two-dimensional (2D) periodically polarity inverted (PPI) ZnO structures are fabricated on (0001) Al2O3 substrates. For the selection of Zn- and O-polarity of ZnO films, patterned CrN buffer layers and Al2O3 substrates are used, respectively. The periodical change of the polarity is clearly confirmed by the polarity sensitive piezoresponse microscopy images, which are evidences for the successful fabrication of periodical polarity inversion structures. Cathodoluminescence investigation revealed that both polar layers have high crystal quality with strong free exciton emission. Moreover, 2D PPI ZnO structures with subnanometer scale periodicity are demonstrated by using the holographic lithography.

Effect of anion-to-cation supplying ratio on the surface morphology of AlN films grown on ZnO substrates at low temperature

The authors investigated the evolution of surface morphology of AlN films grown on ZnO substrates at low temperature (LT) (400°C) as a function of anion/cation supplying ratio (V/III ratio). Unlike the well-known favorable growth conditions for high-temperature growth, smooth-surface LT-AlN layers were obtained under the O-polar surface, stoichiometric, and N-rich conditions. LT-AlN layers revealed smooth surface (roughness in root mean square=0.20nm for AlN on O-polar ZnO and 0.44nm for AlN on Zn-polar ZnO) and quite low etch-pit density (∼2×106cm−2 for AlN∕Zn-polar ZnO).

A STUDY ON THE INDIUM-INDUCED VARIATIONS IN PHOTOLUMINESCENCE PROPERTIES OF INDIUM-DOPED ZINCOXIDE NANORODS

Indoped ZnO nanorods (ZnO:In NRs) were grown on Si(111) substrates by using AuGe as a catalyst. In-concentration was controlled as high as 0.33 at.%. The length L to diameter D relationship of NRs revealed that the growth mechanism should be explained in terms of not a simple vapor–liquid–solid (VLS) mechanism but a diffusion-induced growth model. In-induced changes have been investigated from the viewpoint of photoluminescence (PL) property. At room temperature, an increase of extrinsic carrier concentration and interaction with excitons were estimated from the blueshift of peak position and decrease of luminescence intensity. Also, narrow linewidth of low-temperature PL spectra characterized the high structural quality of ZnO:In NRs. We have assigned several PL lines and confirmed the assignment by using excitation power and temperature dependence PL. Considerable evidence of crystal quality degradation was not observed from both measurements; however, we could observe that a defect and donor-bound-exciton complex dominate the PL spectrum. ZnO:In NRs shows good optical quality within our experimental range, and this result strongly supports the feasibility of In-doping to enhance the electrical property of ZnO-based nanostructure.