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1.
The growth of cubic GaN on 3C-SiC/Si(100) by metal-organic chemical vapor deposition (MOCVD) under various growth temperatures, thicknesses of 3C-SiC, and V/III ratios was studied. The fractions of cubic and hexagonal phases in the films were estimated from the integrated x-ray diffraction intensities of the cubic (002) and hexagonal (1011) planes. A smooth SiC layer, a high growth temperature, and a moderate V/III ratio are three key factors for the nucleation of the cubic phase and its subsequent growth. Hexagonal GaN with its c-axis perpendicular to the substrate preferentially grows at the low temperature of 750°C. The inclusion of the cubic phase increases with increasing growth temperature. The optimum growth conditions for dominant cubic GaN formation were a growth temperature of 950°C, a 1.5 μm thick SiC layer, and a V/III ratio of 1500. With these growth conditions, a cubic GaN layer with the cubic component of 91% was obtained.  相似文献   

2.
立方GaAs(100)衬底上制备的GaN薄膜多为立方结构且立方相为亚稳相,采用水平常压MOCVD方法在立方GaAs(100)衬底上制备出了GaN薄膜.XRD测试表明,薄膜具有单一的相.结合对工艺条件的分析,认为薄膜具有六方结构.最后,通过Raman光谱测试,证实在立方GaAs衬底上制备出了单相六方GaN薄膜.还对立方GaAs衬底上制备出六方GaN薄膜的原因进行了讨论.  相似文献   

3.
GaN films have been deposited on GaAs(lOO) substrates by a novel growth technique, hot plasma chemical vapor deposition. A radio frequency N plasma source with high power, up to 5 kW, provides an abundance of nitrogen atoms during growth. In addition, strong ultraviolet emissions from the hot plasma irradiate onto the substrate and promote the dissociation of triethylgallium, this results in growth of GaN at very low temperature (even at room temperature). In this paper, we describe the characteristics of hot nitrogen plasma and present the results of the low temperature growth of GaN. In addition, we have investigated the effects of the nitridation of GaAs substrates. Reflection high energy electron diffraction indicates the formation of a surface cubic nitrided layer on the pretreated GaAs. The GaN films grown on fully nitrided GaAs(l00) substrates are of dominantly cubic structures.  相似文献   

4.
The pure cubic GaN(c-GaN) has been grown on (001) GaAs substrates by ECR-PAMOCVD technique at low temperature using TMGa and high pure N2 as Ga and N sources,respectively.The effects of substrate pretreatment conditions on quality of cubic GaN epilayer are investigated by the measurements of TEM and XRD.It is found that hydrogen plasma cleaning,nitridation and buffer layer growth are very important for quality of cubic GaN epilayer.  相似文献   

5.
Nanoscale spatial phase modulation of GaN grown on a 355-nm period array of V-grooves fabricated in a Si(001) substrate is reported. Orientation-dependent selective nucleation of GaN in metal-organic vapor phase epitaxy begins from the opposing Si{111} sidewalls and rapidly fills each V-groove. At the initial stages of growth, the GaN deposited on the sidewalls has hexagonal phase with the c-axis normal to the Si{111}. As the growth continues, the filling of the V-groove over these misaligned hexagonal phase regions results in a transition to a cubic phase with its principal crystal axes parallel to those of the Si substrate. In a cross-sectional view perpendicular to the grooves, the defected hexagonal phase region and the clean cubic phase region above it form a boundary at the inside of each V-groove which is parallel to the Si{111} sidewalls. The GaN surface is almost planarized for only 75-nm deposition and is parallel to the original [001] plane of the Si substrate. The GaN clearly exhibits nanoscale spatial phase modulation with a periodic separation of hexagonal and cubic crystal structures across the groove direction for 600-nm deposition, implying a possibility of cubic phase GaN on an isolated single V-groove fabricated in a Si(001) substrate for monolithic integration. The structural/optical properties and stress measurements of this phase-modulated GaN grown on a nanoscale faceted Si surface are presented.  相似文献   

6.
Thick GaN films were grown on the sapphire substrate by hydride vapour phase epitaxy. The properties of GaN films were found to be significantly influenced by the duration of exposing the sapphire substrate to ammonia prior to the GaN growth initiation. The crystalline quality of GaN films revealed by high resolution X-ray diffraction were strongly dependent on the nitridation time, which determined substrate surface topography. The different nitridation schemes strongly affected the morphology of GaN overlayers resulting in the blue shift of the main excitonic peak in photoluminescence spectra at room temperature.  相似文献   

7.
采用同步辐射XRD极图法对低温MOCVD生长的GaN缓冲层薄膜进行了研究.极图研究表明,低温GaN薄膜中除有正常结晶外还存在一次孪晶和二次孪晶.在χ固定为55°时的{111}ψ扫描中发现了异常的Bragg衍射峰,表明GaN/GaAs(001)低温生长中孪晶现象非常明显.GaAs(001)表面上出现的{111}小面极性会在生长初期影响孪晶成核,实验结果表明孪晶更易在{111}B面即N面上成核.  相似文献   

8.
The effect of in-situ thermal cycle annealing (TCA) has been investigated for GaN growth on GaAs(lOO), GaAs(111) and sapphire substrates. X-ray diffractometry (XRD) and surface morphology studies were performed for this purpose. Enhanced cubic phase characteristics were observed by employing annealingfor GaN layers grown on (001) GaAs. The thickness of the layer subject to annealing is critical in determining the phase of the subsequently grown layer. Thin initial layers appear to permit maintenance of the cubic phase characteristics shown by the substrate, while hexagonal phase characteristics are manifested for thick initial layers. Higher temperature of annealing of thick pre-annealed layers results in changes from mixed cubic/hexagonal phase to pure hexagonal phase. Growth on GaAs(111) substrates showed single cubic phase characteristics and similar enhancement of crystal quality by using TCA as for layers on GaAs(OOl). Micro-cracks were found to be present after TCA on GaAs(lll) substrates. Thermal cycling also appears to be beneficial for layers grown on sapphire substrates.  相似文献   

9.
We are reporting the first comprehensive investigation of the structural properties of cubic GaN grown on (111) GaAs substrates by low-pressure metalorganic chemical vapor deposition. The minimum full width at half maximum (FWHM) of the x-ray diffraction (XRD) peak of (111) GaN was found to be ∼12 min. The use of low temperature GaN buffers helps to reduce the FWHM of the XRD. Cross-sectional transmission electron microscopy (XTEM) revealed the presence of columnar structures in the GaN film with widths of the order of 500A. Selected area electron diffraction (SAD) patterns at the interface confirmed that cubic (111) GaN was grown in-plane with the (111) GaAs substrate. Highresolution transmission electron microscopy (HRTEM) showed that the interface characteristics of GaN on (111)A GaAs substrate were better than those of the GaN on (lll)B GaAs substrate.  相似文献   

10.
Porous and sub‐micrometer tubes made of textured GaN nanoparticles have been synthesized by an in situ chemical reaction and characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence (PL) and Raman spectroscopies. The in situ reaction involves thermal decomposition and nitridation of 1D gallium oxyhydroxide (GaOOH) at temperatures in the range of 700–900 °C. The 1D shape of the precursor GaOOH is maintained in the resultant GaN tubes. The GaN nanocrystals (estimated to be about 15 nm in size) are found to be highly oriented with respect to each other in the tube structure, with the [110] GaN direction parallel to the tube axis. The growth mechanism of the tube structure has also been studied. β‐Ga2O3 is found to be an intermediate phase between the starting GaOOH precursor and the final GaN product. The growth mechanism involves decomposition of GaOOH, which produces β‐Ga2O3 tubes with hollow interiors, and nitridation of β‐Ga2O3, which leads to growth of textured GaN nanocrystals. Based on the growth mechanism, tubular structures with either quasi‐circular or rectangular cross section are selectively synthesized by controlling the heating rate and calcination temperature. This in situ chemical reaction method provides a new route for synthesizing 1D hollow nanostructures.  相似文献   

11.
We study the plasma-assisted molecular beam epitaxy of cubic GaN on GaAs(OOl) substrates by means ofin-situ reflection high-energy electron diffraction. The epilayers are characterized by x-ray diffraction, photoluminescence, and Hall measurements, and it is found that the overall best films are grown under a N/Ga ratio close to one. For anin-situ determination of the N/Ga ratio, the growth kinetics is studied via surface reconstruction transitions. The effective N flux giving rise to growth is measured using the transient behavior of the half-order diffraction streak intensity for various plasma operating conditions.  相似文献   

12.
用电子束蒸发方法在Si(111)村底蒸发了Au/Cr和Au/Ti/AI/Ti两种金属缓冲层,然后在金属缓冲层上用气源分子束外延(GSMBE)生长GaN.两种缓冲层的表面部比较平整和均匀,都是具有Au(111)面掸优取向的立方相Au层.在Au/Cr/Si(111)上MBE生长的GaN,生长结束后出现剥离.在Au/Ti/Al/Ti/Si(111)上无AIN缓冲层直接生长GaN,得到的是多品GaN;先在800℃生长一层AIN缓冲层,然后在710℃生长GaN,得到的足沿GaN(0001)面择优取向的六方相GaN.将Au/Ti/Al/Ti/Si(111)在 800℃下退火20min,金属层收缩为网状结构,并且成为多晶,不再具有Au(111)方向择优取向.  相似文献   

13.
通过在自制的电子回旋共振等离子体增强金属有机物化学气相沉积 (ECR -PEMOCVD)系统上装配反射高能电子衍射仪 (RHEED) ,对外延GaN生长过程进行原位监测。通过分析研究RHEED图像确定衬底清洗、氮化、缓冲层生长、外延层生长的合适条件  相似文献   

14.
15.
研究了用金属有机物气相外延(MOVPE)方法在GaAs(001)衬底上生长的立方相GaN(c-GaN)外延层的光辅助湿法腐蚀特性,并和生长在蓝宝石(0001)衬底上的六方相GaN(h-GaN) 外延层的光辅助湿法腐蚀特性进行了比较.实验发现c-GaN膜的暗态电流和光电流的变化不同于h-GaN膜的腐蚀电流的变化规律.对引起上述差异的原因进行了简单的讨论.  相似文献   

16.
High quality GaN films have been grown on sapphire substrates (C face and A face) by atmospheric pressure metalorganic chemical vapor deposition (MOCVD) using a new buffer layer. With our reactor configuration and growth parameters, a GaN film grown on a single GaN buffer layer appears opaque with high density of hexagonal pits. Using a single A1N buffer layer results in extremely nonuniform morphology with mirror-like areas near the edge of the substrates and opaque areas in the center. The double buffer layer we report here, with GaN as the first layer and A1N as the second, each with an optimized thickness, leads to mirror-like films across the entire substrate. Scanning electron microscopy, photoluminescence, x-ray diffraction, and van der Pauw geometry Hall measurement data are presented to establish the quality of our films. The mechanism for this new buffer layer is also discussed.  相似文献   

17.
The structural properties and surface morphology of AlGaN/GaN structures grown on LiGaO2 (LGO), sapphire, and hydride vapor phase epitaxy (HVPE)-grown GaN templates are compared. AlGaN grown on LGO substrates shows the narrowest x-ray full width at half maximum (FWHM) for both symmetric 〈00.4〉 and asymmetric 〈10.5〉 reflections. Atomic force microscopy (AFM) analysis on AlGaN surfaces on LGO substrates also show the smoothest morphology as determined by grain size and rms roughness. The small lattice mismatch of LGO to nitrides and easily achievable Ga-polarity of the grown films are the primary reasons for the smoother surface of AlGaN/GaN structure on this alternative substrate. Optimizations of growth conditions and substrate preparation results in step flow growth for an AlGaN/GaN structure with 300 Å thick Al0.25Ga0.75N on 2.4 μm thick GaN. A high III/V flux ratio during growth and recently improved polishing of LGO substrates aids in promoting two dimensional step flow growth. The GaN nucleation layer directly on the LGO substrate showed no evidence of mixed phase cubic and hexagonal structure that is typically observed in the nucleation buffer on sapphire substrates. Cross-sectional high-resolution transmission electron microscopy (HRTEM) was performed on an AlGaN/GaN heterostructure grown on LGO. The atomic arrangement at the AlGaN/GaN interface was sharp and regular, with locally observed monolayer and bilayer steps.  相似文献   

18.
The nitridation of the electrochemically deposited Ga-based compound material on graphene on insulator towards the formation of GaN/graphene hybrid structure was studied by varying the nitridation time and temperature. First, the growth of Ga-based compounds which contains GaON and Ga2O3 on multi-layer graphene on SiO2/Si using a mixture of NH4NO3 and Ga(NO3)3 by a simple two terminal electrochemical deposition at room temperature was performed. Then, the conversion of the grown structures to the crystalline GaN structure was carried out by nitridating the grown structures in NH3 gas. The properties of the grown structures were critically influenced by the studied nitridation parameters. The complete transformation to hexagonal GaN was achieved at nitridation temperature of 1100 °C and time of above 60 min due to the observation of significant diffraction peaks which correspond to hexagonal GaN planes. Meanwhile no diffraction peaks of GaON and Ga2O3 structure were observed. Temperature and time are the key parameters in a nitridation process where the ammoniation rate of GaON and deoxidization rate of Ga2O3 to generate gaseous Ga2O, increase with temperature and time. It was speculated that a complete transformation can not be realized without a complete ammoniation of GaON and deoxidization of Ga2O3. The change of morphological structures was also observed due to both reactions. The presented method demonstrates the feasibility to realize GaN/ graphene hybrid structure on insulator which is highly demanded in fabricating optoelectronic and sensing devices.  相似文献   

19.
基于热力学平衡理论,对在电子回旋共振等离子体增强金属有机化学气相沉积系统中的GaN薄膜生长给出了一个化学平衡模型.计算表明,GaN生长的驱动力Δp是以下生长条件的函数:Ⅲ族输入分压,输入Ⅴ/Ⅲ比,生长温度.计算了六方和立方GaN的生长相图,计算结果和我们的实验结果显示出一定的一致性.通过分析,解释了高温和高Ⅴ/Ⅲ比生长条件适合六方GaN的原因.上述模型可以延伸到用于GaN单晶薄膜生长的类似系统中.  相似文献   

20.
立方相GaN的持续光电导   总被引:1,自引:1,他引:0  
研究了金属有机物化学气相外延 (MOVPE)方法生长的非故意掺杂的立方相 Ga N的持续光电导效应 .在六方相 Ga N中普遍认为持续光电导效应与黄光发射有关 ,而实验则显示在立方 Ga N中 ,持续光电导效应与其中的六方相 Ga N夹杂有关系 ,而与黄光发射没有关系 .文中提出 ,立方相 Ga N与其中的六方相 Ga N夹杂之间的势垒引起的空间载流子分离是导致持续光电导现象的物理原因 .通过建立势垒限制复合模型 ,解释了立方相 Ga N的持续光电导现象的物理过程 ,并对光电导衰减过程的动力学作了分析 .对实验数据拟合的结果证明以上的模型和推导是与实验相符的 .  相似文献   

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