Diethylzinc Flow Research Articles

Evolution of the local structure and crystal phase for thin ZnGaO films grown by metal organic chemical vapor deposition

A systematic investigation is reported to comprehend the atomic and crystal structure of several thin ZnGaO films grown by metal organic chemical vapor deposition method using different flow rates of diethylzinc (DEZn) while keeping triethylgallium and oxygen flow rates constant. The x-ray absorption fine structure analysis has indicated that the local structure of Ga absorbing atom is close to that of β-Ga2O3 at a lower DEZn flow rate of 30 sccm and transforming to ZnGa2O4 structure at higher 60 sccm. There is a certain proportion of Ga ions that occupies the tetrahedral sites. The ratios of tetrahedral and octahedral Ga species (Ga(t)/Ga(o)) are found to be within 5.5–8.8%. The x-ray diffraction patterns showed the crystal structure of ZnGaO films gradually evolving from monoclinic to cubic phase with an increase of DEZn flow rates from 30 sccm to 60 sccm. One film prepared at 40 sccm displays the best crystalline quality and the other grown at 50 sccm exhibits excellent smooth surface having the lowest root mean square value with a roughness of 0.42 nm. The correlation between atomic and crystal structure and the growth is helpful to understand the formation of single-crystalline ZnGa2O4 and its physical mechanism.

Growth and characteristics of p-type doped GaAs nanowire * * Project supported by the National Natural Science Foundation of China (Nos. 61376019, 61504010, 61774021) and the Fund of State Key Laboratory of Information Photonics and Optical Communications (Beijing University of Posts and Telecommunications), China (Nos. IPOC2017ZT02, IPOC2017ZZ01).

The growth of p-type GaAs nanowires (NWs) on GaAs (111) B substrates by metal-organic chemical vapor deposition (MOCVD) has been systematically investigated as a function of diethyl zinc (DEZn) flow. The growth rate of GaAs NWs was slightly improved by Zn-doping and kink is observed under high DEZn flow. In addition, the I–V curves of GaAs NWs has been measured and the p-type dope concentration under the II/III ratio of 0.013 and 0.038 approximated to 1019–1020 cm−3.

Epitaxial Growth of ZnGa2O4: A New, Deep Ultraviolet Semiconductor Candidate

ZnGaO films were grown on c-plane sapphire substrates by metal organic chemical vapor deposition using diethylzinc (DEZn), triethylgallium (TEGa), and oxygen. The flow rate of DEZn was 10–60 sccm, and those of TEGa and oxygen were held constant. The ZnGaO film prepared at a DEZn flow rate of 10 sccm adopted a (201)-oriented single-crystalline β-Ga2O3 phase, whereas those prepared at 30–60 sccm exhibited a (111)-oriented single-crystalline ZnGa2O4 phase. On the basis of Hall measurements, ZnGaO films (10 sccm DEZn) possessed very poor electrical properties, which were similar to those of β-Ga2O3. On the other hand, the carrier concentration in ZnGaO films increased from 1.94 × 1014 to 6.72 × 1016 cm–3, and the resistivity decreased from 5730 to 67.9 Ω-cm when increasing the DEZn flow rate from 30 to 60 sccm. According to compositional analyses, the improved electrical properties of ZnGaO films upon increasing DEZn flow rate from 30 to 40 sccm are due to the increasing Zn content, and the enhancement from ...

Effect of VI/II gas ratio on the properties of MOCVD grown ZnO nanostructures

In the present work, various nanostructures of zinc oxide were grown on quartz substrates using metal organic chemical vapor deposition technique. The growth was carried out at 450 °C and at atmospheric pressure using diethyl zinc and tert-butanol as zinc (group II) and oxygen (group VI) sources, respectively. The VI/II gas ratio was varied by varying the diethyl zinc flow rates from 20 to 35 sccm, and keeping the flow rate of t-butanol fixed at 60 sccm. Effects of this VI/II gas ratio on the structural, micro structural and optical properties of the zinc oxide nanostructures were discussed and a possible growth mechanism explaining the micro structural transition was proposed. At low diethyl zinc flow rate the grains were oriented along the c-axis, while higher flow rate of diethyl zinc promoted three dimensional growths resulting in sheet-like structures. The significant effects of variation of VI/II gas ratio on the micro structure of zinc oxide could be understood from the formation of various nanostructures including grain-like and sheet-like structures.

The effects of zinc-doping on the composition of InGaAsP layers grown by MOCVD

We report on the effects of Zn-doping using diethylzinc (DEZn) on the growth of In1−xGaxAsyP1−y quaternary layers (x=0.18–0.41 and y=0.34–0.76) by metalorganic chemical vapour deposition. Independent of the quaternary layer compositions, a systematic reduction (increase) in Indium (Gallium) was observed. This was accompanied by a reduction in the overall growth rate, and increased tensile strain, with increasing DEZn flow. In contrast, the dependence of arsenic/phosphorus incorporation on DEZn flow was found to depend on the surface stoichiometry. We show quantitatively that the observed tensile strain can be explained by compositional variations caused by the Zn-doping process. These results suggest that DEZn affects both homogeneous and heterogeneous processes during the growth of InGaAsP layers.

Spatial atmospheric atomic layer deposition of InxGayZnzO for thin film transistors.

We have investigated the nucleation and growth of InGaZnO thin films by spatial atmospheric atomic layer deposition. Diethyl zinc (DEZ), trimethyl indium (TMIn), triethyl gallium (TEGa), and water were used as Zn, In, Ga and oxygen precursors, respectively. The vaporized metal precursors have been coinjected in the reactor. The metal composition of InGaZnO has been controlled by varying the TMIn or TEGa flow to the reactor, for a given DEZ flow and exposure time. The morphology of the films changes from polycrystalline, for ZnO and In-doped ZnO, to amorphous for In-rich IZO and InGaZnO. The use of these films as the active channel in TFTs has been demonstrated and the influence of In and Ga cations on the electrical characteristics of the TFTs has been studied.

Developing an epitaxial growth process for ZnO by MOCVD using real-time spectroscopic ellipsometry

Real-time diagnostics are an essential tool in the development and improvement of growth processes for new materials. Here we use real-time spectroscopic polarimetric observations of zinc oxide deposition, and a chemical model derived therefrom, to develop a method of growing dense, two-dimensional zinc oxide epitaxially on sapphire by metalorganic chemical vapor deposition. With the transition between deposition and etching being 13% in the diethylzinc flow rate, it is unlikely that we would have discovered this process without the use of real-time spectroscopic ellipsometry. New photoluminescence data support our conclusion that using this cyclical growth process yields improved material.

Realization and Manipulation of ZnO Nanorod Arrays on Sapphire Substrates Using a Catalyst-Free Metalorganic Chemical Vapor Deposition Technique

Single-crystalline ZnO nanorod arrays (ZNRs) were grown by metalorganic chemical vapor deposition on ZnO buffer/sapphire substrate without using any metal catalyst. The density of vertically aligned ZNRs was found to govern by the morphology and thickness of buffer layer. That is to say, the ZnO buffer layer can be used as the nucleation template to control the growth direction and density of the ZNRs. In addition, by controlling the diethyl zinc flow rate, we can manipulate the size, crystal, and optical quality of ZNRs. Finally, the possible growth mechanism of ZNRs was discussed in detail.

Self-limiting growth of ZnO films on (0 0 0 1) sapphire substrates by atomic layer deposition at low temperatures using diethyl-zinc and nitrous oxide

Atomic layer deposition (ALD) of zinc oxide (ZnO) films on (0 0 0 1) sapphire substrates was conducted at low temperatures by using diethyl-zinc (DEZn) and nitrous oxide (N 2O) as precursors. It was found that a monolayer-by-monolayer growth regime occurred at 300 °C in a range of DEZn flow rates from 5.7 to 8.7 μmol/min. Furthermore, the temperature self-limiting process window for the ALD-grown ZnO films was also observed ranging from 290 to 310 °C. A deposition mechanism is proposed to explain how saturated growth of ZnO is achieved by using DEZn and N 2O. Transmission spectroscopic studies of the ZnO films prepared in the self-limiting regime show that the transmittances of ZnO films are as high as 80% in visible and near infrared spectra. Experimental results indicate that ZnO films with high optical quality can be achieved by ALD at low temperatures using DEZn and N 2O precursors.

Effects of Growth Conditions on Structural Properties of ZnO Nanostructures on Sapphire Substrate by Metal–Organic Chemical Vapor Deposition

ZnO was grown on sapphire substrate by metal–organic chemical vapor deposition using the diethylzinc (DEZn) and oxygen (O2) as source chemicals at 500 °C. Influences of the chamber pressure and O2/DEZn ratio on the ZnO structural properties were discussed. It was found that the chamber pressure has significant effects on the morphology of ZnO and could result in various structures of ZnO including pyramid-like, worm-like, and columnar grain. When the chamber pressure was kept at 10 Torr, the lowest full width at half-maximum of ZnO (002) of 175 arc second can be obtained. On the other hand, by lowering the DEZn flow rate, the crystal quality of ZnO can be improved. Under high DEZn flow rate, the ZnO nanowall-network structures were found to grow vertically on the sapphire substrate without using any metal catalysts. It suggests that higher DEZn flow rate promotes three-dimensional growth mode resulting in increased surface roughness. Therefore, some tip on the ZnO surface could act as nucleation site. In this work, the growth process of our ZnO nanowall networks is said to follow the self-catalyzed growth mechanism under high-DEZn flow rate.

Controllable p-type doping of GaAs nanowires during vapor-liquid-solid growth

We report on controlled p-type doping of GaAs nanowires grown by metal-organic vapor-phase epitaxy on (111)B GaAs substrates using the vapor-liquid-solid growth mode. p-type doping of GaAs nanowires was realized by an additional diethyl zinc flow during the growth. Compared to nominally undoped structures, the current increases by more than six orders of magnitude. The transfer characteristics of fabricated nanowire metal-insulator-semiconductor field-effect transistor devices proved p-type conductivity. By adjusting the II/III ratio, controlled doping concentrations from 4.6×1018 up to 2.3×1019 cm−3 could be achieved at a growth temperature of 400 °C. The doping concentrations were estimated from electrical conductivity measurements applied to single nanowires with different diameters. This estimation is based on a mobility versus carrier concentration model with surface depletion included.

Low temperature photoluminescence characteristics of Zn-doped InP grown by metalorganic chemical vapor deposition

Zn-doped InP layers were obtained by two different doping techniques: in situ doping by low pressure metalorganic chemical vapor deposition, and thermal diffusion from a Zn-containing film. Their low temperature photoluminescence (PL) characteristics were studied, and compared. In Zn-diffused InP, the deep donor to acceptor transition was the most dominant transition and other transitions such as the band edge transition and the band to band or shallow donor to acceptor transition were not observed at the excitation power of 10 mW. On the other hand, well resolved band edge peaks and the band or shallow donor to acceptor transition peak were observed for in situ Zn doped InP, implying that less interstitial Zn atoms were generated during in situ doping. Saturation of the hole concentration at 1.5×1018 cm3 was observed in in situ Zn doped InP, and the changes in PL characteristics at the saturation level were extensively studied. Two new deep bands at 0.88–1.0 eV and 1.21–1.27 eV were observed, and the intensity of the lower energy band increased with diethylzinc flow rate. The lower energy band was observed even at room temperature, and it is presumed to be related with the saturation of hole concentration.