Nitrogen Incorporation Efficiency Research Articles

An innovative gas inlet design in a microwave plasma chemical vapor deposition chamber for high-quality, high-speed, and high-efficiency diamond growth

A novel design of the gas inlet system in a diamond microwave plasma chemical vapor deposition growth chamber has been reported in this paper. The design is targeting for high-quality, high-speed, and high-efficiency diamond material fabrication. By introducing a gas inlet hole into the susceptor, we expand the ways of gas introduction for diamond growth. After extensive numerical and experimental investigation, we have found that the introduction of methane and doping gas inlet from the hole of below while the hydrogen from the top is feasible for realizing the target. The growth and doping species could be confined around the substrate, making efficient usage of the precursors. The plasma state change caused by the difference of the gas inlet modes has been ascribed to the resulted gas distribution in the chamber. The measured growth rate has been increased to 32 μm h−1, which is 16 times higher than traditional gas inlet configuration. Meanwhile, a large improvement of the nitrogen doping concentration has been achieved. Besides, with the increase of growth rate and nitrogen incorporation efficiency, the crystal quality and surface morphology keep in an acceptable degree. In this mode, the dual gas flow system can perfectly solve the contradiction among the crystal quality, growth rate, and doping efficiency, commonly existing during the material fabrication process, the chamber contamination could be significantly suppressed due to the constrained distribution of methyl and doping species, making the fabrication cost much lower. The results of repetitive experiments indicate that other residual impurities present in the chamber of microwave plasma chemical vapor deposition could likely regulate the threshold concentration of nitrogen required for accelerating the growth rate during the nitrogen doped diamond growth, which have a significant effect on the diamond growth.

Nitrogen-related point defects in homoepitaxial diamond (001) freestanding single crystals

Controllability of nitrogen doping, types of nitrogen-related defects, and their charge states in homoepitaxial diamond (001) crystals were investigated. For these purposes, 15N-doped 12C-enriched free-standing chemical vapor deposited diamond (001) crystals were grown through long-time growth using 12C-enriched methane as the carbon source gas and 15N-enriched molecular nitrogen as the nitrogen source gas. The formation of non-epitaxial crystallites and growth hillocks was suppressed by the application of the oxygen-adding growth condition. Nitrogen was incorporated uniformly into the crystals, with a concentration variation of less than 10%. About 70% of the total nitrogen was substitutional nitrogen in a neutral charge state Ns0. Hydrogen was incorporated at approximately the same concentration as nitrogen. Both NV and NVH centers were predominantly negatively charged defect structures, i.e., NV− and NHV− centers. The concentrations of NHV− centers were less than 5% of the total nitrogen concentration. Nitrogen concentration in diamond crystals was controlled by changing the N/C gas ratio over a wide doping range from 10 ppb to 10 ppm. Nitrogen incorporation efficiency was found to be (1.5 ± 0.5) × 10−4 in this study.

Effect of growth interruption on Ga(N, As)/Ga(As, Sb)/Ga(N, As) type-II-“W” quantum well heterostructures

Ga(N,As)/Ga(As,Sb)/Ga(N,As) type-II-“W” quantum well heterostructures and Ga(As,Sb)/Ga(N,As) type-II double quantum well heterostructures have been grown by metal organic vapour phase epitaxy (MOVPE) on GaAs-substrate. In particular the influence of growth interruptions on the interface morphology and the nitrogen incorporation efficiency have been studied. Ga(N,As)/Ga(As,Sb)/Ga(N,As) double quantum well structures have been characterized by high resolution x-ray diffraction, scanning transmission electron microscopy and photoluminescence spectroscopy. The internal interfaces were investigated with atomic force microscopy after application of a wet chemical etching technique that allows selective etching of all layers above. We observed a drastic effect of growth interruption duration on the nitrogen incorporation into Ga(N,As): Without growth interruption the nitrogen content was lowered strongly when grown on Ga(As,Sb) QWs. With increasing growth interruption an increase in nitrogen content is visible. The buried Ga(As,Sb) interface first showed a smoothing followed by a subsequent roughening due to the formation of holes of the Ga(As,Sb)-layer with longer growth interruption durations.

Ga(N,P) Growth on Si and Decomposition Studies of the N–P Precursor Di-tert-butylaminophosphane (DTBAP)

III/V semiconductors containing small amounts of nitrogen (dilute nitrides) are promising for applications such as lasers and solar cells. Metal–organic vapor-phase epitaxy (MOVPE) is a widely used technique for growing III/V semiconductors on an industrial scale, and the growth of dilute nitrides with this method is promising for later successful market entry. The main issues of dilute nitrides are carbon incorporation and low nitrogen incorporation efficiency of the conventional N precursors. Due to the high N incorporation efficiency and the low decomposition temperature of the As and N precursor di-tert-butylaminoarsane (DTBAA), a similar P- and N-containing precursor, di-tert-butylaminophosphane (DTBAP), was synthesized and purified on a laboratory scale. Growth studies using this precursor were carried out in this work realizing Ga(N,P)/GaP multi quantum wells on Si and GaP substrates. The structures show evidence of N incorporation, and good layer structures were confirmed by high-resolution X-ray diffraction. Following the influence of different growth parameters on the N incorporation, the growth rate and surface morphology were characterized to set a foundation for possible growth applications in the future. DTBAP shows many advantages over the conventional N source 1,1-dimethylhydrazine (UDMHy) such as a much lower decomposition temperature of 310 °C and the realization of Ga(N,P) layers grown at temperatures as low as 475 °C with a high N incorporation of over 10%. Furthermore, the gas-phase decomposition of DTBAP has been studied with a real-time fast Fourier transform quadrupole ion trap mass spectrometer attached inline to the MOVPE reactor. The decomposition of DTBAP behaves very similarly to the As analogue DTBAA. On the one hand, the tert-butyl groups attached to DTBAP decompose radically, leading to the formation of isobutane, and decompose, on the other hand, by β-H elimination, leading to the formation of isobutene. Furthermore, the decomposition products indicate a direct cleavage of the P–N bond of the molecule, resulting in the formation of aminyl radicals (NH2•). The formation of NH2• explains the high N incorporation efficiency of DTBAP at low temperatures as well as its limitations due to loss of NH3 at higher temperatures.

In English

Codoped by nitrogen and zirconium ions titania thin films have been obtained by sol-gel and pulse laser deposition (PLD) methods to investigate the influence of zirconium ions as well as the synthesis procedure on the efficiency of nitrogen incorporation into semiconductive lattice that, in turns, effected on the film activity under ultraviolet and visible light. The composition of the films and the synthesis methods changed the optical properties of the materials as namely almost no effect of both doping agents on the band gap energy value was noted for the films obtained by pulse laser deposition technique, while its sharp narrowing was observed for nitrogen doped titania sol-gel sample. Additionally, the high absorption in the visible part of the spectra with the different maxima were registered for sol-gel films. Substitutional and interstitial nitrogen incorporation occurred in the case of sol-gel titania doped by both doping agents and only nitrogen, respectively. However, both types of nitrogen atoms were detected by X-ray photoelectron spectroscopy measurements for the laser deposited films and the relative intensity of its state was dependent whether single or double doping agents was used. Incorporation of each doping agent in titania matrix positively influenced on the photocatalytic activity of the sol-gel films under both ultraviolet and visible light. In the case of pulse laser deposited films, the presence of double doping agent stimulated the activity under UV light and the doping only by nitrogen led to the increase of photoactivity in visible light.

Nitrogen incorporation into GaAsN and InGaAsN layers grown by liquid‐phase epitaxy

AbstractThis paper presents the comparison of nitrogen incorporation in GaAsN and InGaAsN layers grown on GaAs substrate from Ga‐ and In‐rich solution, respectively, by liquid‐phase epitaxy. Polycrystalline GaN has been used as a source of nitrogen in two cases. The initial epitaxy temperature has been varied in the temperature range 600‐550 °C. Nitrogen content in Ga1‐xAsNx grown layers has been determined to be in the range 0.1‐0.5%. Higher nitrogen incorporation efficiency has been found for quaternary InGaAsN layers grown under carefully chosen lattice matched conditions. The incorporation of nitrogen into GaAsN and InGaAsN layers has been study by vibrational mode absorption spectroscopy. Nitrogen‐induced vibration mode near 472 cm‐1 has been registered in GaAsN samples. Preferential In‐N bonds and the formation of N‐centred In3Ga1 clusters have been identified for lattice matched to GaAs epitaxial InGaAsN layers. Electrical properties of the samples have been characterized by temperature‐dependent Hall effect measurements. Nominally undoped GaAsN and InGaAsN grown layers are n‐type with Hall concentration about one order of magnitude higher in comparison to layers not containing nitrogen. Thermally activated increase in the free carrier concentration at temperatures higher than 150 K is observed which indicates the presence of N‐related deep donor levels below dilute nitride conduction band edge. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Dilute nitride InGaAsN/GaAs V-groove quantum wires emitting at 1.3 μm wavelength at room temperature

Site-controlled InGaAsN quantum wires (QWRs) emitting at 1.3 μm at room temperature were grown on V-grooved GaAs substrates by modulated-flux metallorganic vapor phase epitaxy. The nonplanar substrate template is shown to enhance the nitrogen uptake, evidenced by a redshift in photoluminescence wavelength twice larger for the QWRs than for the adjacent quantum well regions. The mechanism of this increase in nitrogen incorporation efficiency, achieved without degradation in optical properties, is explained by the extended gradient of In content at the step-rich QWR interfaces.

Nitrogen Doping in Low-Temperature Halo-Carbon Homoepitaxial Growth of SiC

In this work, nitrogen doping was investigated during the low-temperature halo-carbon epitaxial growth of 4H-SiC on Si- and C-faces. The dependencies of nitrogen incorporation on nitrogen flow rate, Si/C ratio, growth rate, and temperature were investigated. It was established that the efficiency of nitrogen incorporation for the C-face growth at 1300 °C is higher than that for the Si-face for a wide range of the growth conditions. Seeming deviation of the Si/C ratio dependence from the “site-competition” trend confirmed the critical role of the silicon vapor condensation during the low-temperature epitaxy. Opposite trends for the nitrogen doping dependence on the growth rate were observed on the Si- and C-faces. Finally, a complex temperature dependence of the nitrogen doping in the temperature range from 1300 to 1450 0C was observed.

Effects of hydrogen on the properties of SiC crystals grown by physical vapor transport: Thermodynamic considerations and experimental results

Thermodynamic analysis of the effects of hydrogen addition to the growth ambient during physical vapor transport growth of SiC is presented. In the presence of hydrogen, the efficiency of carbon transport should greatly improve due to the interaction between hydrogen and graphite resulting in formation of hydrocarbons and due to more congruent evaporation of the SiC source material. The changes induced by hydrogen are more pronounced at lower growth temperatures and higher background pressures. A temperature range of 2000–2350 °C and total pressures of 10–100 Torr were considered. Among the consequences of the increased C/Si ratio in the vapor phase, the marked decrease of the nitrogen incorporation efficiency and the suppression of formation of deep traps related to Si-rich growth conditions are expected to be the most prominent. Growth experiments with hydrogen concentrations in the 0–50% range show that indeed the nitrogen concentration decreases by several times and the density of all electron traps in SiC becomes lower by about an order of magnitude with the addition of hydrogen.

Growth dynamics and optimization of Ga(In)AsN/GaAs towards 1.3 μm and 1.55 μm

It is demonstrated that a nitrogen supply, manifested as both a direct nitrogen beam from a rf-activated plasma source and dispersive nitrogen radicals from the growth-chamber background, is appropriate for the growth of GaAs-based nitrides. The nitrogen incorporation efficiency shows a linear relationship with increasing rf power when the nitrogen is supplied dispersively, and a saturation behavior when the nitrogen is supplied as a direct nitrogen beam. The indium composition causes a decrease in the nitrogen incorporation efficiency, which is suspected to be brought about by the increase of the growth rate due to the indium flux, because our experiments have proven that the nitrogen composition of GaAsN epilayers apparently decreases as the growth rate increases. It is more controllable to fix the indium flux first than to fix the nitrogen source condition, so as to facilitate wavelength control. The temperature window for the growth of quality nitride is concluded to be between 440 °C and 500 °C. For a quantum well with a certain well width, it is better to add more indium and less nitrogen to reach the desired wavelength in order that the quality of the InGaAs material is kept acceptable.

Control of nitrogen incorporation in Ga(In)NAs grown by metalorganic vapor phase epitaxy

We report on our studies of the nitrogen incorporation behavior in GaNAs bulk layers and GaInNAs quantum wells, grown by metalorganic chemical vapor deposition. By high-resolution x-ray diffraction measurements on GaNAs, we observe that the nitrogen incorporation efficiency increases with increasing tertiary-butyl-arsine flow up to a certain threshold. Results on GaInNAs quantum wells (QWs) confirm this trend. Finally, we link the optical quality of these quantum wells to the abruptness of the QWs and the nitrogen content.

Epitaxial Growth and Characterization of 4H-SiC(11–20) and (03–38)

ABSTRACTHomoepitaxial growth, impurity doping, and diode fabrication on 4H-SiC(11–20) and (03–38) have been investigated. Although the efficiency of nitrogen incorporation is higher on the non-standard faces than on (0001), a low background doping concentration of 2∼3×1014 cm-3 can be achieved. On these faces, boron and aluminum are less effectively incorporated, compared to the growth on off-axis (0001). 4H-SiC(11–20) epilayers are micropipe-free, as expected. More interestingly, almost perfect micropipe closing has been realized in 4H-SiC (03–38) epitaxial growth. Ni/4H-SiC(11–20) and (03–38) Schottky barrier diodes showed promising characteritics of 3.36 kV-24 mΩcm2 and 3.28 kV–22 mΩcm2, respectively. The breakdown voltage of 4H-SiC(03–38) Schottky barrier diodes was significantly improved from 1 kV to above 2.5 kV by micropipe closing.

GaAsN-on-GaAs MBE using a DC plasma source

A new dc plasma source for MBE growth of GaAsN layers is suggested. The efficiency of nitrogen incorporation, crystal perfection, surface morphology, and luminescent properties of the epilayers vs. operation conditions of the source are studied.

Nitrogen incorporation during 4H-SiC epitaxy in a chimney CVD reactor

Nitrogen incorporation is studied during epitaxial chemical vapour deposition (CVD) of 4H-SiC in a vertical, hot-wall CVD reactor. The nitrogen doping dependencies on input C/Si ratio, growth temperature and process pressure are investigated under the process conditions leading to growth rates in the range of 15–30 μm/h. The nitrogen incorporation is observed to be a thermally activated process with a higher apparent activation energy for the Si-face than for the C-face. The site-competition principle is well followed at C/Si ratios higher than 0.3, whereas the nitrogen doping becomes less sensitive to the C/Si ratio on both the Si- and the C-faces at C/Si ratios below 0.3. The pressure has a strong effect on the nitrogen incorporation efficiency, allowing lower doping at the lower pressure. The influence of the growth parameters on the nitrogen incorporation is closely related both to the epitaxial growth mechanisms and to the surface kinetics on the different polarity SiC faces. The doping mechanisms are analysed taking into account the gas-phase chemistry and the surface kinetics.

MBE growth of (In)GaAsN on GaAs using a constricted DC plasmasource

(In)GaAsN epilayers were grown on GaAs substrates by molecular beam epitaxy (MBE) with a DC constricted-plasma source. Nitrogen incorporation efficiency, crystalline quality, surfacemorphology and luminescent properties of the epilayers werestudied and correlated with various operation regimes of the source.The nitrogen incorporation efficiency grows withincreasing plasma discharge current.The maximum nitrogen concentration in the epilayer is as high as3.7 %.GaAsN as thick as 0.35 µm can be pseudomorphically grown on GaAs, andphotoluminescence is observed at room temperature.The crystalline quality and surface morphology of an epilayer can also be improvedby reducing the ion damage at low plasma discharge current.The DC constricted-plasma source is a promising alternative nitrogenplasma source for investigating InGaAsN materials.

Molecular-beam epitaxy of (Al)GaAsN using ammonia as the nitrogen source

Molecular-beam epitaxy of an (Al)GaAsN alloy was demonstrated using uncracked ammonia as the nitrogen source. It was found that the efficiency of nitrogen incorporation into the alloy layers was dramatically enhanced when aluminum flux was supplied during growth. The nitrogen composition of an Al0.07Ga0.93As1−yNy layer grown at 580 °C was approximately 100 times larger than that of a GaAs1−yNy layer grown at the same growth condition without the aluminum supply. The nitrogen incorporation into the AlxGa1−xAs1−yNy layers was found to be proportional to the aluminum composition x. The activation energy of nitrogen incorporation was measured to be 195 kJ/mol.

Growth rate dependence of nitrogen incorporation in reactively sputtered FeXN films for recording head poles

In this paper we show that the efficiency of nitrogen incorporation in reactively sputtered FeAlN and FeN films is strongly dependent on the growth rate of the films. Efficiency is defined as the amount of nitrogen incorporated for a given ratio of arriving iron atoms to arriving nitrogen atoms. These findings are in contrast to previous work, which has suggested the amount of nitrogen incorporated in the films should be determined by this arrival flux ratio alone, and independent of growth rate. This difference may be due to the larger range of deposition rates explored in this work. A simple and phenomenological kinetic model of the deposition process is used to rationalize the observed behavior. This behavior has important consequences for scaling the deposition of FeXN up to commercial deposition rates while maintaining soft magnetic properties. This is because the amount of nitrogen incorporated has a strong effect on the soft properties of these pole materials.

Layer-by-layer growth of AlN and GaN by molecular beam epitaxy

The conditions for obtaining layer-by-layer growth of (0001) AlN and GaN with wurtzite structure in molecular beam epitaxy (MBE) have been determined by studying reflection high-energy electron diffraction (RHEED) oscillations. For both materials, the growth conditions are optimized when the metal/nitrogen ratio is close to unity. Atomic hydrogen has been found to enhance significantly the AlN growth rate. This effect is tentatively attributed to an increase in the nitrogen incorporation efficiency in the presence of hydrogen.

Rumen fermentation, bacterial and total volatile fatty acid (TVFA) production rates in cattle fed on urea-molasses-mineral block licks supplement

Of twenty rumen fistulated calves, four were allocated randomly to each of five tests. Animals were offered only wheat straw ad lib (T1), or in addition were supplemented with concentrate mixture (T2), or any one of three different types of UMMB-lick type A (T3), type B (T4) and type C (T5). A metabolism trial was conducted. Bacterial production rate (BPR) and total volatile fatty acid (VFA) production rate were estimated with an isotope dilution technique using 35S sodium sulfate and 14C sodium acetate, respectively.Nitrogen (N) balance in T1 animals were negative but, positive in other treatment groups. Total-N, ammonia-N, non-protein-N, TCA-precipitable-N in rumen on treatment groups T3 to T5 were comparable with T2 but higher than T1 (P < 0.01). Ammonia levels in rumen improved significantly on UMMB supplementation. Bacterial pool size and BPR were improved three-fold (P < 0.01) in T2 to T5 in comparison with T1. BPR per unit of digestible organic matter intake was higher on UMMB-lick type B and C than type A. Total VFA concentration, production rate and molar proportion of individual VFAs were higher (P < 0.01) and acetate to propionate ratio as well as non-glucogenic ratio were lower (P < 0.01) on treatment groups T3, T4 and T5 than on T1, while comparable with T2. YATP (gram of bacteria per mole of ATP) was 5.7, 8.9, 7.4, 9.7 and 9.6 in T1 to T5, respectively. Nitrogen incorporation efficiency by rumen bacteria was lower (P < 0.01) on supplementation of UMMB-licks compared to concentrate supplement. In conclusion, it would be possible for synergy in N and energy availability from UMMB-lick supplementation to wheat straw to stimulate microbial yield and fermentation in rumen like that from conventional concentrate supplement. The composition of UMMB-lick type B and type C was found to be better than type A in improving the microbial yield.

Nitrogen doping in AlGaP grown by organometallic vapor phase epitaxy using tertiarybutylamine as nitrogen source

Doping characteristics of nitrogen in AlGaP grown by organometallic vapor phase epitaxy (OMVPE) are investigated by using tertiarybutylamine (TBNH 2) as the nitrogen source. The nitrogen concentration increases with increasing TBNH 2 vapor phase composition. The nitrogen incorporation efficiency is raised with the introduction of aluminum, which may be due to the strong Al-N bond energy. A high crystalline quality of N-doped AlGaP layer for greenish color emission with nitrogen concentration as high as 10 20 cm -3 can be obtained by using TBNH 2 as the nitrogen source.