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研究了具有不同台阶数目的AlGaN插入层对在6H-SiC衬底上利用金属有机物气相外延(MOVPE)生长的GaN体材料残余应力和表面形貌的影响.高分辨率X射线衍射测试表明样品的c轴晶格常数随台阶数目的增多而增大;低温光荧光谱中GaN发光峰也随着台阶数目增多而发生蓝移,这些变化都反映出GaN中残余张应力的减小.此外,原子力显微镜测试表明样品表面起伏和粗糙度也都随着插入层的引入和台阶数目的增多得到了明显的改善.
关键词:
残余应力
表面形貌
SiC衬底
AlGaN插入层 相似文献
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Improved Surface Characteristics and Contact Performance of Epitaxial p-AlGaN by a Chemical Treatment Process 下载免费PDF全文
The comparative study of epitaxial 380-run-thick p-Al0.091 Ga0.909 N materials without and with special surface chemical treatment is systematically carried out. After the treatment process, the deep level luminous peak in the 10 K photoluminescence spectrum is eliminated due to the decrease of surface nitrogen vacancy VN related defective sites, while the surface root-mean-square roughness in atomic force microscopy measurement is decreased from 0.395nm to 0.229nm by such a surface preparation method. Furthermore, the performance of surface contact with Ni/Au bilayer metal fihns is obviously improved with the reduction of the Schottky barrier height of 55meV. The x-ray photoelectron spectroscopy (XPS) results show a notable surface element content change after the treatment which is considered to be the cause of the above-mentioned surface characteristics improvement. 相似文献
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研究了不同浓度的F- 和Ce3 +对磷酸三钙 (Ca3 (PO4) 2 ,TCP)的水解过程和水解产物的影响。XRD及IR实验结果表明 ,TCP在NaF溶液中的水解产物为羟基磷灰石 (Ca1 0 (PO4) 6(OH) 2 ,HAP)和氟基磷灰石 (Ca1 0 (PO4) 6F2 ,FAP)的混合物。氟离子浓度越高 ,FAP的含量越多。TCP水解过程的pH值变化随氟离子的起始浓度不同而不同。氟离子浓度越高 ,pH值越低。TCP在CeCl3 溶液中的水解产物为铈取代的羟基磷灰石 (CexCa1 0 -y(PO4) 6-z(OH) 2 ,Ce HAP)。溶解实验表明 ,氟处理比铈处理更有效地增强了TCP水解产物的抗酸性。当F -浓度为 0 1%或Ce3 +浓度为 5× 10 - 2 %时 ,TCP水解产物的抗酸性最强 相似文献
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Direct observation of the carrier transport process in InGaN quantum wells with a pn-junction 下载免费PDF全文
A new mechanism of light-to-electricity conversion that uses InGaN/GaN QWs with a p-n junction is reported.According to the well established light-to-electricity conversion theory,quantum wells(QWs) cannot be used in solar cells and photodetectors because the photogenerated carriers in QWs usually relax to ground energy levels,owing to quantum confinement,and cannot form a photocurrent.We observe directly that more than 95% of the photoexcited carriers escape from InGaN/GaN QWs to generate a photocurrent,indicating that the thermionic emission and tunneling processes proposed previously cannot explain carriers escaping from QWs.We show that photoexcited carriers can escape directly from the QWs when the device is under working conditions.Our finding challenges the current theory and demonstrates a new prospect for developing highly efficient solar cells and photodetectors. 相似文献
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The green light emitting diodes(LEDs)have lower quantum efficiency than LEDs with other emission wavelengths in the visible spectrum.In this research,a novel quantum well structure was designed to improve the electroluminescence(EL)of green InGaN-based LEDs.Compared with the conventional quantum well structure,the novel structure LED gained 2.14times light out power(LOP)at 20-mA current injection,narrower FWHM and lower blue-shift at different current injection conditions. 相似文献
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We have successfully prepared GaN based high electron mobility transistors(HEMTs)on metallic substrates transferred from silicon substrates by electroplating technique.GaN HEMTs on Cu substrates are demonstrated to basically have the same good electric characteristics as the chips on Si substrates.Furthermore,the better heat dissipation of HEMTs on Cu substrates compared to HEMTs on Si substrates is clearly observed by thermoreflectance imaging,showing the promising potential for very high-power and high-temperature operation.This work shows the outstanding ability of HEMT chips on Cu substrates for solving the self-heating effect with the advantages of process simplicity,high yield,and low production requirement. 相似文献
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Characterization of the N-polar GaN film grown on C-plane sapphire and misoriented C-plane sapphire substrates by MOCVD 下载免费PDF全文
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
20.
Visualizing light-to-electricity conversion process in InGaN/GaN multi-quantum wells with a p-n junction 下载免费PDF全文
Absorption and carrier transport behavior plays an important role in the light-to-electricity conversion process, which is difficult to characterize. Here we develop a method to visualize such a conversion process in the InGaN/GaN multiquantum wells embedded in a p-n junction. Under non-resonant absorption conditions, a photocurrent was generated and the photoluminescence intensity decayed by more than 70% when the p-n junction out-circuit was switched from open to short. However, when the excitation photon energy decreased to the resonant absorption edge, the photocurrent dropped drastically and the photoluminescence under open and short circuit conditions showed similar intensity. These results indicate that the escaping of the photo-generated carriers from the quantum wells is closely related to the excitation photon energy. 相似文献