p-type Zn1−xMgxO films with Sb doping by radio-frequency magnetron sputtering
TL;DR: Sb-doped Zn1-xMgxO films were grown on c-plane sapphire ubstrates by radio-frequency magnetron sputtering as mentioned in this paper, revealing a hole concentration of 10(15)-10(16) cm(-3) and a mobility of 0.6-4.5 cm(2)/V s.
Abstract: Sb-doped Zn1-xMgxO films were grown on c-plane sapphire ubstrates by radio-frequency magnetron sputtering. The p-type conduction of the films (0.05 <= x <= 0.13) was confirmed by Hall measurements, revealing a hole concentration of 10(15)-10(16) cm(-3) and a mobility of 0.6-4.5 cm(2)/V s. A p-n homojunction comprising an undoped ZnO layer and an Sb-doped Zn0.95Mg0.05O layer shows a typical rectifying characteristic. Sb-doped p-type Zn1-xMgxO films also exhibit a changeable wider band gap as a function of x, implying that they can probably be used for fabrication of ZnO-based quantum wells and ultraviolet optoelectronic devices. (c) 2006 American Institute of Physics.
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TL;DR: Transparent conductors (TCs) have a multitude of applications for solar energy utilization and for energy savings, especially in buildings as discussed by the authors, which leads naturally to considerations of spectral selectivity, angular selectivity, and temporal variability of TCs, as covered in three subsequent sections.
1,471 citations
TL;DR: In this paper, the authors discuss p-type ZnO materials: theory, growth, properties and devices, comprehensively, and summarize the growth techniques and properties of P-type materials.
329 citations
01 Jan 2013
TL;DR: In this article, the authors discuss p-type ZnO materials: theory, growth, properties and devices, comprehensively, and summarize the growth techniques for p- type ZnOs.
Abstract: Abstract In the past 10 years, ZnO as a semiconductor has attracted considerable attention due to its unique properties, such as high electron mobility, wide and direct band gap and large exciton binding energy. ZnO has been considered a promising material for optoelectronic device applications, and the fabrications of high quality p-type ZnO and p–n junction are the key steps to realize these applications. However, the reliable p-type doping of the material remains a major challenge because of the self-compensation from native donor defects (V O and Zn i ) and/or hydrogen incorporation. Considerable efforts have been made to obtain p-type ZnO by doping different elements with various techniques. Remarkable progresses have been achieved, both theoretically and experimentally. In this paper, we discuss p-type ZnO materials: theory, growth, properties and devices, comprehensively. We first discuss the native defects in ZnO. Among the native defects in ZnO, V Zn and O i act as acceptors. We then present the theory of p-type doping in ZnO, and summarize the growth techniques for p-type ZnO and the properties of p-type ZnO materials. Theoretically, the principles of selection of p-type dopant, codoping method and X Zn –2V Zn acceptor model are introduced. Experimentally, besides the intrinsic p-type ZnO grown at O-rich ambient, p-type ZnO (MgZnO) materials have been prepared by various techniques using Group-I, IV and V elements. We pay a special attention to the band gap of p-type ZnO by band-gap engineering and room temperature ferromagnetism observed in p-type ZnO. Finally, we summarize the devices based on p-type ZnO materials.
308 citations
TL;DR: In this article, the effects of Mg concentrations on microstructure, surface topography and optical properties of ZnO thin films have been measured by X-ray diffraction (XRD), atomic force microscope (AFM), UV-vis spectrophotometer, and fluorophotometer (FL), respectively.
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TL;DR: A first-principles investigation, based on density functional theory, produces strong evidence that hydrogen acts as a source of conductivity: it can incorporate in high concentrations and behaves as a shallow donor.
Abstract: Zinc oxide, a wide-band-gap semiconductor with many technological applications, typically exhibits n-type conductivity. The cause of this conductivity has been widely debated. A first-principles investigation, based on density functional theory, produces strong evidence that hydrogen acts as a source of conductivity: it can incorporate in high concentrations and behaves as a shallow donor. This behavior is unexpected and very different from hydrogen's role in other semiconductors, in which it acts only as a compensating center and always counteracts the prevailing conductivity. These insights have important consequences for control and utilization of hydrogen in oxides in general.
2,970 citations
TL;DR: Wurtzitic ZnO is a widebandgap semiconductor which has many applications, such as piezoelectric transducers, varistors, phosphors, and transparent conducting films as discussed by the authors.
Abstract: Wurtzitic ZnO is a wide-bandgap (3.437 eV at 2 K) semiconductor which has many applications, such as piezoelectric transducers, varistors, phosphors, and transparent conducting films. Most of these applications require only polycrystalline material; however, recent successes in producing large-area single crystals have opened up the possibility of producing blue and UV light emitters, and high-temperature, high-power transistors. The main advantages of ZnO as a light emitter are its large exciton binding energy (60 meV), and the existence of well-developed bulk and epitaxial growth processes; for electronic applications, its attractiveness lies in having high breakdown strength and high saturation velocity. Optical UV lasing, at both low and high temperatures, has already been demonstrated, although efficient electrical lasing must await the further development of good, p-type material. ZnO is also much more resistant to radiation damage than are other common semiconductor materials, such as Si, GaAs, CdS, and even GaN; thus, it should be useful for space applications.
2,573 citations
TL;DR: In this paper, the authors study the intrinsic defect physics of ZnO and find that ZnOs cannot be doped p type via native defects, despite the fact that they are shallow donors.
Abstract: ZnO typifies a class of materials that can be doped via native defects in only one way: either n type or p type. We explain this asymmetry in ZnO via a study of its intrinsic defect physics, including ${\mathrm{Zn}}_{\mathrm{O}},$ ${\mathrm{Zn}}_{i},$ ${\mathrm{V}}_{\mathrm{O}},$ ${\mathrm{O}}_{i},$ and ${V}_{\mathrm{Zn}}$ and n-type impurity dopants, Al and F. We find that ZnO is n type at Zn-rich conditions. This is because (i) the Zn interstitial, ${\mathrm{Zn}}_{i},$ is a shallow donor, supplying electrons; (ii) its formation enthalpy is low for both Zn-rich and O-rich conditions, so this defect is abundant; and (iii) the native defects that could compensate the n-type doping effect of ${\mathrm{Zn}}_{i}$ (interstitial O, ${\mathrm{O}}_{i},$ and Zn vacancy, ${V}_{\mathrm{Zn}}),$ have high formation enthalpies for Zn-rich conditions, so these ``electron killers'' are not abundant. We find that ZnO cannot be doped p type via native defects $({\mathrm{O}}_{i},{V}_{\mathrm{Zn}})$ despite the fact that they are shallow (i.e., supplying holes at room temperature). This is because at both Zn-rich and O-rich conditions, the defects that could compensate p-type doping ${(V}_{\mathrm{O}}{,\mathrm{}\mathrm{Zn}}_{i},{\mathrm{Zn}}_{\mathrm{O}})$ have low formation enthalpies so these ``hole killers'' form readily. Furthermore, we identify electron-hole radiative recombination at the ${V}_{\mathrm{O}}$ center as the source of the green luminescence. In contrast, a large structural relaxation of the same center upon double hole capture leads to slow electron-hole recombination (either radiative or nonradiative) responsible for the slow decay of photoconductivity.
1,724 citations
TL;DR: In this article, a wide gap II-VI semiconductor alloy, MgxZn1−xO, was proposed for the fabrication of heteroepitaxial ultraviolet light emitting devices based on ZnO.
Abstract: We propose a widegap II–VI semiconductor alloy, MgxZn1−xO, for the fabrication of heteroepitaxial ultraviolet light emitting devices based on ZnO. The c-axis oriented MgxZn1−xO films were epitaxially grown by pulsed laser deposition on ZnO epitaxial films and sapphire (0001) substrates using ceramic targets. Solid solution films were prepared with Mg content up to x=0.33, achieving a band gap of 3.99 eV at room temperature. MgO impurity phase segregated at x⩾0.36. Lattice constants of MgxZn1−xO films changed slightly (∼1%), increasing in a axis and decreasing in c-axis direction with increasing x. These films showed ultraviolet photoluminescence at energies from 3.36 (x=0) to 3.87 eV (x=0.33) at 4.2 K.
1,441 citations
TL;DR: In this paper, the structural and optical properties of II-VI oxide alloys, MgxZn1−xO and CdyZn 1−yO, grown by pulsed-laser deposition, were described.
Abstract: We describe the structural and optical properties of II–VI oxide alloys, MgxZn1−xO and CdyZn1−yO, grown by pulsed-laser deposition. Single-phase alloyed films of (Mg,Zn)O and (Cd,Zn)O with c-axis orientations were epitaxially grown on sapphire (0001) substrates. The maximum magnesium and cadmium concentrations (x=0.33 and y=0.07, respectively) were significantly larger than the thermodynamic solubility limits. The band gap energies systematically changed from 3.0 (y=0.07) to 4.0 eV (x=0.33) at room temperature. The photoluminescence peak energy deduced at 4.2 K could be tuned from 3.19 to 3.87 eV by using Cd0.07Zn0.93O and Mg0.33Zn0.67O 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 Cd0.01Zn0.99O grown on a lattice-matched ScAlMgO4 substrate.
633 citations