Electron Cyclotron Resonance Plasma Enhanced Metal Organic Chemical Vapor Deposition Research Articles

Low temperature epitaxial technology for GaN-based materials

<p indent="0mm">The band gap of GaN-based semiconductor materials covers the entire visible light band and has excellent physical and chemical properties, which makes it widely used in the fabrication of optoelectronic devices, power electronic devices, and radio frequency and microwave devices. Traditional GaN-based materials are usually epitaxially grown on high-temperature-resistant single-crystalline substrates such as sapphire, silicon, or silicon carbide using metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or hydride vapor phase epitaxy (HVPE). These epitaxial techniques usually use high temperature to crack the precursors involved in the reaction. With the deepening of informatization and intelligentization, the common demands for low-cost and flexibility of opto(electronic) devices have emerged. On one hand, the display technology is a key link to realize information exchange and intelligence. Moving towards an intelligent society requires further reduction of the display cost per unit area. At the same time, the wearable and portable flexible display technology also has broad application prospects. In addition, solid-state lighting has gradually penetrated into every corner of human life with the improvement of device performance. The application scenarios are rich and colorful. Judging from this, low-cost surface light sources will be a strong competitor for the next generation of lighting technology routes. On the other hand, reducing the fabrication cost of electronic devices per unit area also needs more attention in the future. For example, flexible electronic skin has broad and huge application prospects in artificial limbs, robotics, medical detection and diagnosis, etc., which has also spawned the demand for low-cost flexible sensors. It can be seen that the common requirements of the above applications for core components are low cost and flexibility, which is also one of the main development directions of the next generation of (opto)electronic devices. Amorphous substrates (such as glass, plastic, metal, polyethylene terephthalate (PET), polydimethylsiloxane (PDMS), etc.) that are cheap and easy to fabricate are ideal choices, but a significant disadvantage is that amorphous substrates cannot withstand high growth temperatures. Therefore, the need for low-temperature epitaxy of GaN-based materials has arisen, that is, a kind of epitaxy equipment that can use external electric field energy to crack the reaction precursor at low temperatures. So far, a variety of low-temperature epitaxial technologies have been developed based on the physical vapor deposition (PVD) and the chemical vapor deposition (CVD), and preliminary research results have been obtained. The PVD techniques include reactive magnetron sputtering, plasma-assisted MBE (PA-MBE), pulsed laser deposition (PLD), pulsed sputtering deposition (PSD), laser MBE (LMBE), etc. The CVD techniques include remote plasma CVD (RPCVD), migration enhanced afterglow CVD (MEA-CVD), remote plasma-enhanced MOCVD (RPEMOCVD), radical-enhanced MOCVD (REMOCVD), electron cyclotron resonance plasma-enhanced MOCVD (ECR-PEMOCVD), inductive coupled plasma MOCVD (ICP-MOCVD), etc. In this paper, the two types of low-temperature epitaxial technologies are introduced in detail, including the device structure, working conditions and related epitaxial growth results, and the characteristics of each type of technology are summarized. Finally, the development prospect of low temperature epitaxial technologies is prospected, and the focus of future research is pointed out. We hope this work can provide a useful reference for the low temperature epitaxy research of GaN-based materials.

Study on the Performance Impact of Introducing an InN Buffer Layer at Various Deposition Temperatures on InN Film Grown by ECR-PEMOCVD on Free-Standing Diamond Substrate

In this study, InN films are grown at a relatively low temperature by electron cyclotron resonance plasma-enhanced metal organic chemical vapor deposition (ECR-PEMOCVD) on free-standing diamond substrates. Due to the high lattice mismatch rate between InN film and the free-standing diamond substrate, the function of a buffer layer is to build a bridge between the substrate and film to reduce the lattice mismatch between them. Therefore, here, we study the performance impact of introducing an InN buffer layer at various deposition temperatures and explore the optimal buffer layer deposition temperature used to grow relatively high-quality InN films. The experimental results show that when an InN buffer layer is introduced at a deposition temperature of 100 °C, the growth direction of the InN film is perpendicular to the substrate with a high c-axis preferred orientation, the roughness of the surface is minimal, and the particle sizes are consistent with growth in the same direction. Additionally, the carrier mobility is highest, and the carrier concentration is lowest compared with other conditions.

Impact of the Deposition Temperature on the Structural and Electrical Properties of InN Films Grown on Self-Standing Diamond Substrates by Low-Temperature ECR-MOCVD

The progress of InN semiconductors is still in its infancy compared to GaN-based devices and materials. Herein, InN thin films were grown on self-standing diamond substrates using low-temperature electron cyclotron resonance plasma-enhanced metal organic chemical vapor deposition (ECR-PEMOCVD) with inert N2 used as a nitrogen source. The thermal conductivity of diamond substrates makes the as-grown InN films especially attractive for various optoelectronic applications. Structural and electrical properties which depend on deposition temperature were systematically investigated by reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and Hall effect measurement. The results indicated that the quality and properties of InN films were significantly influenced by the deposition temperature, and InN films with highly c-axis preferential orientation and surface morphology were obtained at optimized temperatures of 400 °C. Moreover, their electrical properties with deposition temperature were studied, and their tendency was correlated with the dependence on micro- structure and morphology.

Study on Preparation and Properties of InN Films on Self-Supporting Diamond Substrates Under Different Nitrogen Flows

Several InN film samples with superb properties were prepared on a self-supporting diamond substrate for different nitrogen flow rates using an electron cyclotron resonance plasma-enhanced metal-organic chemical vapor deposition (ECR-PEMOCVD) system. After the InN film samples were obtained, the samples were characterized via reflected high-energy electron diffraction (RHEED), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscope (AFM), and electron probe micro-analysis (EPMA) to study the effect of the nitrogen flow on the quality of the InN films. The experimental results show that the variation in the nitrogen flow has a great impact on the preferential growth of the (0002) crystal plane of the InN thin-film. By increasing the nitrogen flow moderately, the crystal quality of the film is improved. Under the growth condition of appropriate nitrogen flow, InN thin-films with a preferred orientation along the c-axis can be obtained, and the surface of the resulting InN thin-films is relatively flat. However, a high nitrogen flow does not improve the film crystal quality. The results of the experiment and of the analysis show that the InN films prepared with a nitrogen flow rate of 80 sccm have an excellent preferential orientation. The result of the EPMA test shows that the percentages of the In and N atoms in the prepared film samples are close to a ratio of 1:1, and a small amount of metal In droplets is present. In addition, the InN thin-films prepared in such condition have an excellent surface morphology and composition.

Influence of TMGa Flux on the Improvement of GaN Films on Thick Freestanding Diamond Films

High-quality GaN films are deposited on diamond films using an electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition (ECR-PEMOCVD) under the condition of the proper Trimethyl gallium (TMGa) flux. The influence of TMGa flux on the properties of GaN films is systematically investigated by x-ray diffraction analysis (XRD) and atomic force microscopy (AFM). The results show that the high quality GaN films with small surface roughness and high c-orientation are successfully achieved at the optimized flux. The most significant improvements in morphological and structural properties of GaN films are obtained by using a proper TMGa flux

Structural and Electrical Properties of High C-Orientation GaN Films on Diamond Substrates

Preferred orientation GaN films are deposited on freestanding thick diamond films by electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition (ECR-PEMOCVD). The TMGa and N2 are applied as precursors and different N2 flux is used to achieve high quality GaN films. The influence of N2 flux on the properties of GaN films is systematically investigated by x-ray diffraction analysis (XRD), atomic force microscopy (AFM), electron probe microanalysis (EPMA) and Hall Effect Measurement (HL). The results show that the high quality GaN films deposited at the proper N2 flux display a fine structural and electrical property and the Ga/N atomic ratio plays an important role in the electrical property of GaN films.

Low-temperature growth of highly c-oriented GaN films on Cu coated glass substrates with ECR-PEMOCVD

Highly c-axis oriented GaN films were deposited on Cu coated glass substrates using electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition (ECR-PEMOCVD). In-situ reflection high energy electron diffraction (RHEED), X-ray diffraction (XRD) and atomic force microscopy (AFM) were used to systematically analyze the influence of TMGa flux on the crystalline quality of the GaN films. GaN films with strong c-axis preferred orientation were achieved under the optimal TMGa flux of 1.4sccm. Moreover, a strong near band edge (NBE) emission peak located at 354nm was observed in the room temperature PL spectrum for the optimized GaN sample. The GaN/Cu/glass structure shows great potential for application in large area low cost GaN-based LED devices.

Low temperature synthesis of GaN films on ITO substrates by ECR-PEMOCVD

GaN films were deposited on indium tin oxide (ITO) coated glass substrates at various deposition temperatures using an electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition (ECR-PEMOCVD). The TMGa and N2 are applied as precursors of Ga and N, respectively. The crystalline quality and photoluminescence properties of as-grown GaN films are systematically investigated as a function of deposition temperature by means of X-ray diffraction analysis (XRD), reflection high energy electron diffraction (RHEED), atomic force microscopy (AFM), and room temperature photoluminescence (PL). The results show that the dense and uniformed GaN films with highly c-axis preferred orientation are successfully achieved on ITO glass substrates under optimized deposition temperature of 430 °C, and the room temperature PL spectra of the optimized GaN film show an intense near-band-edge luminescence located at 360 nm. The obtained GaN/ITO/glass structure was especially attractive for transparent optoelectronics applications with inexpensive ITO/glass substrate.

Deposition and properties of highly c-oriented of InN films on sapphire substrates with ECR-plasma-enhanced MOCVD

InN films with highly c-axis preferred orientation were deposited on sapphire substrate by low-temperature electron cyclotron resonance plasma-enhanced metal organic chemical vapor deposition (ECR-PEMOCVD). Trimethyl indium (TMIn) and N2 were applied as precursors of In and N, respectively. The quality of as-grown InN films were systematically investigated as a function of TMIn fluxes by means of reflection high-energy electron diffraction (RHEED), X-ray diffraction analysis (XRD), and atomic force microscopy (AFM). The results show that the dense and uniform InN films with highly c-axis preferred orientation are successfully achieved on sapphire substrates under optimized TMIn flux of 0.8 ml·min−1. The InN films reported here will provide various opportunities for the development of high efficiency and high-performance semiconductor devices based on InN material.

Effect of buffer layer on the structural and morphological properties of GaN films grown with ECR-PEMOCVD

Prefer-oriented GaN films are deposited on freestanding thick diamond films by electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition (ECR-PEMOCVD) at various buffer layers. Trimethyl gallium (TMGa) and N 2 are applied as precursors and various buffer layers are used to achieve high quality GaN films. The influence of buffer layers process on the properties of GaN films is systematically investigated by reflection high energy electron diffraction (RHEED), X-ray diffraction analysis (XRD) and atomic force microscopy (AFM). The results show that the high quality GaN films deposited at proper buffer layer process display the fine structural and morphological properties.

Low-temperature growth of highly c-oriented InN films on glass substrates with ECR-PEMOCVD

High quality InN films are deposited with an interlayer of high c-orientation (002) AZO (Aluminium-doped Zinc Oxide; ZnO:Al) films on glass substrates by electron cyclotron resonance plasma-enhanced metal organic chemical vapor deposition (ECR-PEMOCVD) at low temperature. AZO films used as a buffer layer are effective for the epitaxial growth of InN films. The influence of Trimethyl Indium (TMIn) flux on the properties of InN films is systematically investigated by reflection high energy electron diffraction (RHEED), X-ray diffraction analysis (XRD), atomic force microscopy (AFM) and optical transmittance spectra. The results indicate that high quality InN films with high c-orientation and small surface roughness are successfully achieved at an optimized Trimethyl Indium (TMIn) flux of 5.5 sccm. The InN/AZO structures have great potential for the development of full spectra solar cells.

The Preparation and Characteristics of InxGa1−xN (0.06 ≤ x ≤ 0.58) Films Deposited by ECR-PEMOCVD

We investigate the structural property and surface morphology of InxGa1−xN films for In compositions ranging from 0.06 to 0.58, which are deposited by electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition (ECR-PEMOCVD). The results of x-ray diffraction (XRD) in InGaN films confirm that they have excellent c-axis orientation. The In content in the InGaN epilayers is checked by electron probe microanalysis (EPMA), which reveals that In fractions determined by XRD are in good agreement with the EPMA results. Atomic force microscopy measurements reveal that the grown films have a surface roughness that varies between 4.16 and 8.14nm. The results suggest that it is possible to deposit high-c-axis-orientation InGaN films with different In contents.

Highly c-axis oriented GaN films grown on free-standing diamond substrates for high-power devices

GaN films with highly c-axis preferred orientation are deposited on free-standing thick diamond films by low temperature electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition (ECR-PEMOCVD). The TMGa and N 2 are applied as precursors of Ga and N, respectively. The quality of as-grown GaN films are systematically investigated as a function of deposition temperature by means of X-ray diffraction (XRD) analysis, Hall Effect measurement (HL), room temperature photoluminescence (PL) and atomic force microscopy (AFM). The results show that the dense and uniformed GaN films with highly c-axis preferred orientation are successfully achieved on free-standing diamond substrates under optimized deposition temperature of 400 °C, and the room temperature PL spectra of the optimized GaN film show a intense ultraviolet near band edge emission and a weak yellow luminescence. The obtained GaN/diamond structure has great potential for the development of high-power semiconductor devices due to its excellent heat dissipation nature.

Influence of N2 Flux on InN Film Deposition on Sapphire (0001) Substrates by ECR-PEMOCVD

Highly preferred InN films are deposited on sapphire (0001) substrates by electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition (ECR-PEMOCVD) without using a buffer layer. The structure, surface morphological and electrical characteristics of InN are investigated by in-situ reflection high energy electron diffraction, x-ray diffraction, x-ray photoelectron spectroscopy, atomic force microscopy and Hall effect measurement. The quality of the as-grown InN films is markedly improved at the optimized N2 flux of 100 sccm. The results show that the properties of the films are strongly dependent on N2 flux.

Deposition and properties of highly C-oriented GaN films on diamond substrates

High-quality GaN films are deposited on freestanding thick diamond films by electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition (ECR-PEMOCVD). The TMGa flux dependent structural, morphological, and electrical characteristics of GaN films were investigated by x-ray diffraction analysis (XRD), reflection high-energy electron diffraction (RHEED), atomic force microscopy (AFM) and Hall effect measurement. The results indicate that it is feasible to deposit GaN films on freestanding thick diamond films under the proper deposition procedures. The high-quality GaN films with small surface roughness of 4.9 nm and high c-orientation are successfully achieved at the optimized TMGa flux of 0.5 sccm. The GaN/diamond structure has great potential for the development of SAW devices with high frequencies and low insertion.

Effect of Nitridation on GaN Film Grown on Glass Substrate by ECR-PEMOCVD Method

Nitridation of Corning 7101 glass substrate and the following GaN deposition were carried out in a self-developed electron cyclotron resonance plasma enhanced metalorganic chemical vapor deposition (ECR-PEMOCVD) system equipped with in-situ reflection high-energy electron diffraction (RHEED) monitoring. RHEED pattern and X-Ray diffraction (XRD) spectrum showed that the nitridation can effectively improve the C-axis orientation of as-prepared GaN film. Atomic force microscope (AFM) analysis indicated that the average grain size increased significantly with 5 min of nitriding, but degraded as nitriding time increased. The optimum nitriding time was achieved as 5 min. The effect of nitridation on the GaN film deposition and its formation mechanism were discussed.

Deposition of GaN Films on Freestanding CVD Thick Diamond Films

High quality GaN films are deposited on freestanding thick diamond films by electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition (ECR-PEMOCVD). The characteristics of GaN films were investigated by x-ray diffraction analysis (XRD), reflection high energy electron diffraction (RHEED) and atomic force microscopy (AFM). The high quality GaN films with small surface roughness of 8.3 nm and high c-orientation are successfully achieved at the optimized nitriding time with the diamond substrate. These properties of GaN films with small surface smoothness and high c-orientation are well used as piezoelectric films for surface acoustic wave (SAW) devices.

Analysis of diluted magnetic semiconductor GaMnN grown by electron cyclotron resonance-plasma enhanced metal organic chemical vapor deposition

Diluted magnetic semiconductor film GaMnN was grown on sapphire (α-Al2O3) substrate using biscyclopentyldienyl manganese (Cp2Mn), N2 and TEGa by electron cyclotron resonance-plasma enhanced metal organic chemical vapor deposition(ECR-PEMOCVD) . The crystal structure and surface topography of the GaMnN films were characterized by RHEED, XRD and AFM. GaMnN films exhibit good (0002) preferred orientation, showing the films are inclined to c-axis growth and retain good wurtzite structure. The surface topography of GaMnN film is composed of many submicron grains piled in the consistent orientation. The magnetism of films is characterized by SQUID. SQUID shows that the film is ferromagnetic, which comes probably only from the ternary phase GaMnN and the Curie temperature of GaMnN film is higher than 350 K. Moreover, higher Mn concentration can enhance the Curie temperature of the film.

Direct Crystallization and Characterization of Bi3TiTaO9 Thin Films Prepared by Metalorganic Chemical Vapor Deposition

Bi3TiTaO9 (BTT) thin films were prepared on (111)Pt/Ti/SiO2/Si substrate by electron cyclotron resonance plasma-enhanced metalorganic chemical vapor deposition (ECR-MOCVD). BTT thin films deposited at 550°C were found to consist of a single phase of bismuth layer structure by X-ray diffraction (XRD). This temperature was lower than that reported in the data for obtaining single phase SrBi2Ta2O9 (SBT) thin films prepared by MOCVD. Furthermore, the reciprocal space mapping of BTT thin films showed the (103)-preferred orientation of this film, as well as the orientation of SBT thin films. The dielectric constant, εr, and loss tangent, tan δ, of the BTT thin film were 180 and 3% at 1 MHz, respectively. An abrupt increase of the leakage current of this film was observed at about 280 kV/cm.

Effects of Sr/Ti Ratio on the Step Coverage of SrTiO3 Thin Films Fabricated Using Electron Cyclotron Resonance Plasma Enhanced Metal Organic Chemical Vapor Deposition

SrTiO3 thin films were deposited on Si(p-type 100), Pt(1000 Å)/SiO2/Si and stepped Pt(800 Å)/SiO2/Si substrates using electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition (ECR-PEMOCVD) to study the effects of deposition temperature and composition on the properties of SrTiO3 thin films. The crystallinity and dielectric properties of SrTiO3 thin films were improved as the deposition temperature increased. We observed a distinct correlation, not between step coverage and deposition temperature, but between the step coverage and the composition. The composition of the film was changed by changing the flow rate of one of the carrier gas but fixing that of the other, with the deposition temperature fixed at 550°C. The step coverage was improved as the composition (Sr/Ti ratio) increased up to the stoichiometric composition and showed a saturated value of about 55% as the Sr/Ti ratio increased beyond the stoichiometric composition. This correlation was speculated based on the sticking coefficients of the precursor vapors.