Band gap engineering based on MgxZn1−xO and CdyZn1−yO ternary alloy films

Abstract

We describe the structural and optical properties of II-VI oxide alloys, Mg x Zn 1Ϫx O and Cd y Zn 1Ϫy O, grown by pulsed-laser deposition. Single-phase alloyed films of ͑Mg,Zn͒O and ͑Cd,Zn͒O with c-axis orientations were epitaxially grown on sapphire ͑0001͒ substrates. The maximum magnesium and cadmium concentrations ͑xϭ0.33 and yϭ0.07, respectively͒ were significantly larger than the thermodynamic solubility limits. The band gap energies systematically changed from 3.0 (yϭ0.07) to 4.0 eV (xϭ0.33) at room temperature. The photoluminescence peak energy deduced at 4.2 K could be tuned from 3.19 to 3.87 eV by using Cd 0.07 Zn 0.93 O and Mg 0.33 Zn 0.67 O at both ends, respectively. The lattice constants of the a axis were monotonically increasing functions of the concentrations of both alloys. The exciton-phonon coupling strength was determined in Cd 0.01 Zn 0.99 O grown on a lattice-matched ScAlMgO 4 substrate.

Characterization of homoepitaxial p-type ZnO grown by molecular beam epitaxy

“…Heterojunctions and quantum wells can also be fabricated by using MgZnO and CdZnO as the wide-gap and narrow-gap materials, respectively. [15][16][17] The homoepitaxial ZnO thin films were grown by EaglePicher Technologies, LLC ͑Miami, OK͒ in a custom-built MBE system that includes extensive cryogenic shrouding and additional cryopumping. The substrates were 10 mm ϫ10 mmϫ0.5 mm pieces cut from c-plane wafers, which themselves were sliced from bulk, 2-inch-diam ZnO ingots grown by Eagle-Picher using a seeded chemical vapor transport ͑SCVT͒ process.…”

Electrical characteristics of palladium Schottky contacts to hydrogen peroxide treated hydrothermally grown ZnO

“…These properties could lead to the realization of light emitting diodes, transparent thin film transistor, high temperature, high power, high frequency electronic devices, to be used even in space applications and they are fundamental in already established ZnO applications like transparent electrodes in flat panel displays or solar cells. Moreover, the combination of a wide band gap with a high excitonic binding energy and the possibility of growing quantum wells by alloying it with Cd or Mg [7] paves the way to the fabrication of UV lasers based on excitonic recombination which is attractive for implementation of highly efficient opto-electronic devices. Furthermore, processing of ZnO for such devices appears viable: wet chemical etching [8] and low temperature epitaxial growth [9] are possible and there is a well developed technique for growing bulk material, i.e.…”

Microstructure and luminescence dynamics of ZnCdO films with high Cd content deposited on different substrates by DC magnetron sputtering method

“…It should be noted that the band-gap engineering for ZnO is vital for its further progress in optoelectronics: isoelectronic cadmium impurity is an ideal candidate for reducing the band gap of zinc oxide [3]. ZnCdO solid solution has the advantage of tunability of the alloy band gap, allowing larger control over the spectrum of emitted light from near UV to visible [4,5]. Many interesting phenomena like tunable electroluminescence from n-ZnCdO/p-GaN heterojunction [6], luminescence enhancement effect of deuterium in ZnO/ZnCdO quantum wells [7], enhancement of the spontaneous emission rate from ZnCdO quantum wells by surface plasmon coupling [8], rectifying behavior of a p-n junction based on n-Zn 0.94 Cd 0.06 O/p-SiC heterostructures [9] and effect of transparent thin film transistor based on ZnCdO [10] have already been reported.…”