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1.
Integrity of functional self-assembled monolayers on hydrogen-terminated silicon-on-insulator wafers
Silicon-on-insulator (SOI) wafers are commonly used to design microelectronics, energy conversion, and sensing devices. Thin solid films on the surfaces of SOI wafers have been a subject of numerous studies. However, SOI wafers modified by self-assembled monolayers (SAMs) that can also be used as functional device platforms have been investigated to a much lesser extent. In the present work, tert-butoxycarbonyl (t-boc, (CH3)3-C-O-C(O)-)-protected 1-amino-10-undecene monolayers were covalently attached to a H-terminated SOI (1 0 0) surface. The modified wafers were characterized by X-ray photoelectron spectroscopy to confirm the stability of the SAM/Si interface and the integrity of the secondary amine in the SAM. The transmission electron microscopy investigation suggested that this t-boc-protected 1-amino-10-undecene SAM produces atomically flat interface with the 2 μm single crystalline silicon of the SOI wafer, that the SiOx and both available Si/SiOx interfaces are preserved, and that the organic monolayers are stable, with apparent thickness of 1.7 nm, which is consistent with the result of the density functional theory modeling of the molecular features within a SAM. 相似文献
2.
Characterization of the N-polar GaN film grown on C-plane sapphire and misoriented C-plane sapphire substrates by MOCVD
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Xiaotao Hu 《中国物理 B》2022,31(3):38103-038103
Gallium nitride (GaN) thin film of the nitrogen polarity (N-polar) was grown on C-plane sapphire and misoriented C-plane sapphire substrates respectively by metal-organic chemical vapor deposition (MOCVD). The misorientation angle is off-axis from C-plane toward M-plane of the substrates, and the angle is 2° and 4° respectively. The nitrogen polarity was confirmed by examining the images of the scanning electron microscope before and after the wet etching in potassium hydroxide (KOH) solution. The morphology was studied by the optical microscope and atomic force microscope. The crystalline quality was characterized by the x-ray diffraction. The lateral coherence length, the tilt angle, the vertical coherence length, and the vertical lattice-strain were acquired using the pseudo-Voigt function to fit the x-ray diffraction curves and then calculating with four empirical formulae. The lateral coherence length increases with the misorientation angle, because higher step density and shorter distance between adjacent steps can lead to larger lateral coherence length. The tilt angle increases with the misorientation angle, which means that the misoriented substrate can degrade the identity of crystal orientation of the N-polar GaN film. The vertical lattice-strain decreases with the misorientation angle. The vertical coherence length does not change a lot as the misorientation angle increases and this value of all samples is close to the nominal thickness of the N-polar GaN layer. This study helps to understand the influence of the misorientation angle of misoriented C-plane sapphire on the morphology, the crystalline quality, and the microstructure of N-polar GaN films. 相似文献
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Y. Tokuda Y. Matsuoka H. Ueda O. Ishiguro N. Soejima T. Kachi 《Superlattices and Microstructures》2006,40(4-6):268
Electron traps in n-type GaN layers grown homoepitaxially by MOCVD on free-standing GaN substrates have been characterized using DLTS for vertical Schottky diodes. Two free-standing HVPE GaN substrates (A and B), obtained from two different sources, are used. The Si-doped GaN layers with the thickness of 5 μm are grown on an area of 0.9×0.9 cm2 of substrate A and on an area of 1×1 cm2 of substrate B. Two traps labeled B1 and B2 are observed with trap B2 dominant in GaN on both substrates. There exist no dislocation-related traps which have been previously observed in MOCVD GaN on sapphire. This might be correlated to the reduction in dislocation density due to the homoepitaxial growth. However, it is found that there is a large variation, more than an order of magnitude, in trap B2 concentration and that the B2 spatial distributions are different between the two substrates used. 相似文献
5.
S. Joblot Y. Cordier F. Semond S. Chenot P. Venngus O. Tottereau P. Lorenzini J. Massies 《Superlattices and Microstructures》2006,40(4-6):295
We report the realization of an AlGaN/GaN HEMT on silicon (001) substrate with noticeably better transport and electrical characteristics than previously reported. The heterostructure has been grown by molecular beam epitaxy. The 2D electron gas formed at the AlGaN/GaN interface exhibits a sheet carrier density of 8×1012 cm−2 and a Hall mobility of 1800 cm2/V s at room temperature. High electron mobility transistors with a gate length of 4 μm have been processed and DC characteristics have been achieved. A maximum drain current of more than 500 mA/mm and a transconductance gm of 120 mS/mm have been obtained. These results are promising and open the way for making efficient AlGaN/GaN HEMT devices on Si(001). 相似文献
6.
We demonstrate a label-free photonic biosensor with double slots based on micro-ring resonator. The footprint is less than 25 μm × 15 μm. Finite-difference time-domain (FDTD) method is used to analyze the influence of several key parameters on the performance of the double-slots micro-ring resonators. An asymmetric structure is considered for the ring waveguide in order to improve the sensor's bending efficiency. Our numerical analysis shows that the sensitivity of double-slot micro-ring resonator sensor with the radius of 5 μm reaches a value of 708 nm/RIU. The quality factor of 580 and the free spectral range (FSR) of 33 nm are achieved. 相似文献
7.
外延在蓝宝石衬底上的非掺杂GaN研究 总被引:1,自引:0,他引:1
采用改变生长条件的方法制备GaN薄膜,在(0001)面蓝宝石衬底上利用金属有机物化学气相沉积技术制备了不同样品,并借助X射线双晶衍射仪(XRD)、PL谱测试仪和光学显微镜对材料进行了分析。XRD(0002)面和(1012)面测试均表明TMGa流量为70 cm3/min时样品位错密度最低。利用该TMGa流量进一步制备了改变生长温度的样品。XRD和PL谱测试结果表明,提高生长温度有利于提高GaN样品的晶体质量和光学性能。最后,利用光学显微镜对样品的表面形貌进行了分析。 相似文献
8.
采用金属有机化学气相沉积(MOCVD)技术在Si(111)衬底上外延GaN薄膜,对高温AlN(HT-AlN)缓冲层在小范围内低生长压力(6.7~16.6 kPa)条件下对GaN薄膜特性的影响进行了研究。研究结果表明GaN外延层的表面形貌、结构和光学性质对HT-AlN缓冲层的生长压力有很强的的依赖关系。增加HT-AlN缓冲层的生长压力,GaN薄膜的光学和形貌特性均有明显改善,当HT-AlN缓冲层的生长压力为13.3 kPa时,得到无裂纹的GaN薄膜,其(002)和(102)面的X射线衍射峰值半高宽分别为735 arcsec和778 arcsec,由拉曼光谱计算得到的张应力为0.437 GPa,原子力显微镜(AFM)观测到表面粗糙度为1.57 nm。 相似文献
9.
The growth of GaP layer on GaN with and without buffer layers by metal-organic chemical vapour deposition (MOCVD) has been studied. Results indicate that the GaP low temperature buffer layer can provide a high density of nucleation sites for high temperature (HT) GaP growth. These sites can promote the two-dimensional (2D) growth of HT GaP and reduce the surface roughness. A GaP single crystal layer grown at 680°C is obtained using a 40-nm thick GaP buffer layer. The full-width at half-maximum (FWHM) of the (111) plane of GaP layer, measured by DCXRD, is 560 arcsec. The GaP layer grown on GaN without low temperature GaP buffer layer shows a rougher surface. However, the FWHM of the (111) plane is 408 arcsec, which is the indication of better crystal quality for the GaP layer grown on GaN without a low temperature buffer layer. Because it provides less nucleation sites grown at high growth temperature, the three-dimensional (3D) growth is prolonged. The crystalline quality of GaP is lightly improved when the surface of GaN substrate is pretreated by PH3 , while it turned to be polycrystalline when the substrate is pretreated by TEGa. 相似文献
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S.J. Chua S. Tripathy P. Chen E. Takasuka M. Ueno 《Physica E: Low-dimensional Systems and Nanostructures》2005,25(4):356-365
Using near-field scanning optical microscopy (NSOM), we report the spatial distribution of photoluminescence (PL) intensity in III-nitride-based semiconductor layers grown on GaN substrates. Undoped GaN, In0.11Ga0.89N, and In0.13Ga0.87N/GaN multi-quantum wells (MQWs) were grown by metal organic chemical vapor deposition (MOCVD) on freestanding GaN substrates. Micro-Raman spectroscopy has been used to evaluate the crystalline properties of the GaN homoepitaxial layers. The variation of the PL intensity from the NSOM imaging indicates that the external PL efficiency fluctuates from 20% to 40% in the 200 nm InGaN single layer on freestanding GaN, whereas it fluctuates from 20% to 60% in InGaN/GaN MQWs. In the NSOM-PL images, bright island-like features are observed. After deconvolution with the spatial resolution of the NSOM, the size of these features is estimated to be in the range of 150–250 nm. 相似文献
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On semipolar epitaxial ZnO grown by chemical vapor deposition consists of two distinct orientations as evidenced by transmission electron microscopy and X‐ray diffraction. The initially grown ZnO on GaN follows the GaN lattice with the epitaxial relationship of // and The other oriented ZnO domains then grow on faceted with and with good coherency with the ‐oriented grains. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
12.
In this paper we propose a new method for measuring the thickness of the GaN epilayer, by using the ratio of the integrated intensity of the GaN epilayer X-ray diffraction peaks to that of the sapphire substrate ones. This ratio shows a linear dependence on the GaN epilayer thickness up to 2 μm. The new method is more accurate and convenient than those of using the relationship between the integrated intensity of GaN epilayer diffraction peaks and the GaN thickness. Besides, it can eliminate the absorption effect of the GaN epilayer. 相似文献
13.
利用卢瑟福背散射/沟道技术和高分辨率X射线衍射技术对在Si(111)衬底上利用金属有机化合物气相外延技术(MOVPE)生长有多缓冲层的六方GaN外延膜进行结晶品质计算、晶格常数计算和应变分析. 实验结果表明:GaN外延膜的结晶品质为χmin=1.54%,已达到完美晶体的结晶品质(χmin=1%—2%);GaN外延膜的水平方向和垂直方向晶格常数分别为:aepi=0.31903nm,cepi=0.51837nm,基本达到G
关键词:
GaN
高分辨X射线衍射
卢瑟福背散射/沟道
弹性应变 相似文献
14.
Highly-sensitive silicon-on-insulator sensor based on two cascaded micro-ring resonators with vernier effect 总被引:1,自引:0,他引:1
A highly-sensitive integrated optical biosensor based on two cascaded micro-rings resonator (MRR) is investigated theoretically and experimentally. The free spectral ranges (FSRs) of two cascaded micro-rings are designed to be slightly different in order to generate Vernier effect. A preliminary investigation of our sensor with a Q factor of 2 × 104 using different ethanol concentrations shows that the Vernier effect can improve the sensitivity to 1300 nm per refractive index unit (RIU), compared to 62 nm/RIU for a single ring sensor. The sensor also has a large measurement range of refractive index change up to 1.15 × 10− 2 RIU. It can be useful for low-cost and highly-sensitive optical biosensor system. 相似文献
15.
N. Zainal S.V. Novikov A.V. Akimov C.R. Staddon C.T. Foxon A.J. Kent 《Physica B: Condensed Matter》2012,407(15):2964-2966
The dependence of the hexagonal fraction with thickness in MBE-grown bulk cubic (c-) GaN epilayer is presented in this paper. A number of c-GaN epilayers with different thicknesses were characterized via PL and XRD measurements. From the PL spectra, the signal due to h-GaN inclusions increases as the thickness of the c-GaN increases. On the contrary, in the XRD diffractogram, c-GaN shows a dominant signal at all thicknesses, and only a weak peak at ∼35° is observed in the diffractogram, implying the existence of a small amount of h-GaN in the c-GaN layer. The best quality of c-GaN is observed in the first 10 μm of GaN on the top of GaAs substrate. Even though the hexagonal content increases with the thickness, the average content remains below 20% in c-GaN layers up to 50 μm thick. The surface morphology of thick c-GaN is also presented. 相似文献
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G. Pozina C.G. Hemmingsson J.P. Bergman D. Trinh L. Hultman B. Monemar 《Superlattices and Microstructures》2008,43(5-6):605
Freestanding GaN layers of various thicknesses grown by HVPE have been studied by time-resolved spectroscopy combined with structural and electrical measurements. We have observed an increase of the PL lifetime with increasing layer thickness; however, a saturation of the recombination times has been detected for the GaN layers thicker than 400 μm. We explain the observed thickness-dependent behavior of the decay times by competition of two nonradiative mechanisms; namely, for layers with thickness less than 400 μm the main nonradiative channel is related to the structural defects, while in thicker layers the recombination decay time is limited by impurities and/or vacancies. 相似文献
18.
Junping Mei 《Applied Surface Science》2011,257(16):7217-7220
We report the growth of GaN epilayers on the sapphire substrate etched by MOCVD. Sapphire substrate is etched by H3PO4 and NaOH. The Raman scattering spectroscopy and photoetching analyses show that the substrate etched can effectively decrease the residual stress and the dislocations density in these epilayers. The X-ray diffraction analysis shows the process can reduce the value of the FWHM. Therefore, the quality of GaN epilayers should be improved by substrate etched. 相似文献
19.
在柱状图形蓝宝石衬底(PSS-p)和孔状图形蓝宝石衬底(PSS-h)上外延了GaN体材料和LED结构并进行了详细对比和分析.X射线衍射仪(XRD)和原子力显微镜(AFM)测试结果表明,PSS-h上体材料的晶体质量和表面形貌都优于PSS-p上体材料的特性,通过断面扫面电子显微镜(SEM)照片看出PSS-h上GaN的侧向生长是导致这种差异的原因.另外,基于PSS-p和PSS-h上外延的LED材料制作而成的器件结果表明,其20?mA下光功率水平相比普通蓝宝石衬底(CSS)分别提高了46%和33%.通过变温光荧光
关键词:
蓝宝石图形衬底
氮化镓
发光二极管
侧向生长 相似文献
20.
MOCVD生长GaN:Si单晶膜的研究 总被引:4,自引:0,他引:4
获得高质量的n型GaN单晶膜是制作GaN基光电子器件的关键之一。采用立式MOCVD系统生长GaN:Si单晶膜,通过优化生长工艺,获得了电子载流于浓度高达2 ×1019cm-3,迁移率达120cm2/V·s的n型GaN:Si单晶膜;并有效地抑制了GaN中由深能级引起的黄带发射,大大提高带边发光强度。研究结果还表明:随着S掺杂量的增大,GaN:Si单晶膜的电子载流于浓度增加,迁移率下降,X光双晶衍射峰半高宽增大。首次报道了随掺S量增大,GaN:Si单晶膜的生长速率显著下降的现象。 相似文献