共查询到20条相似文献,搜索用时 0 毫秒
1.
S.C. Hung Y.K. Su S.J. Chang S.C. Chen L.W. Ji T.H. Fang L.W. Tu M. Chen 《Applied Physics A: Materials Science & Processing》2005,80(8):1607-1610
GaN hollow nanocolumns were formed by inductively coupled plasma etching. It was found that the tops of the GaN nanocolumns were hexagonal with the c axis perpendicular to the substrate surface. It was also found that the density of the GaN nanocolumns depends strongly on etching parameters, which suggests that the formation of these GaN nanocolumns was not related to the dislocation density in the original GaN epitaxial layers. With an Ar concentration of 42.86%, it was found that the diameter of the whole nanocolumns was around 80 nm and the diameter of the nanocavities inside these nanocolumns was around 40 nm, while the density of the nanocolumns was around 4.4×109 cm-2. PACS 68.65.-K; 61.70.+w; 81.10.BK 相似文献
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Optimization of inductively coupled plasma deep etching of GaN and etching damage analysis 总被引:1,自引:0,他引:1
Inductively coupled plasma (ICP) etching of GaN with an etching depth up to 4 μm is systemically studied by varying ICP power, RF power and chamber pressure, respectively, which results in etch rates ranging from ∼370 nm/min to 900 nm/min. The surface morphology and damages of the etched surface are characterized by optical microscope, scanning electron microscope, atomic force microscopy, cathodoluminescence mapping and photoluminescence (PL) spectroscopy. Sub-micrometer-scale hexagonal pits and pillars originating from part of the structural defects within the original GaN layer are observed on the etched surface. The density of these surface features varies with etching conditions. Considerable reduction of PL band-edge emission from the etched GaN surface indicates that high-density non-radiative recombination centers are created by ICP etching. The density of these non-radiative recombination centers is found largely dependent on the degree of physical bombardments, which is a strong function of the RF power applied. Finally, a low-surface-damage etch recipe with high ICP power, low RF power, high chamber pressure is suggested. 相似文献
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Yongjin Wang Fangren Hu Masashi Wakui Kazuhiro Hane 《Applied Physics A: Materials Science & Processing》2009,97(1):39-43
We report here a top-down process for fabricating a freestanding circular GaN grating. The circular gratings are defined by
electron-beam lithography and realized by fast-atom beam (FAB) etching. The silicon substrate below the GaN grating region
is completely removed to make the circular grating suspended in space. The optical responses of the fabricated GaN gratings
are characterized in reflectance measurements. The polarization-independent responses of circular gratings are experimentally
demonstrated, corresponding well with the theoretical prediction. This work represents an important step in combining GaN-based
material with freestanding nanostructures. 相似文献
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A series of experiments were conducted to systematically study the effects of etching conditions on GaN by a con-venient photo-assisted chemical (PAC) etching method. The solution concentration has an evident influence on the surface morphology of GaN and the optimal solution concentrations for GaN hexagonal pyramids have been identified. GaN with hexagonal pyramids have higher crystal quality and tensile strain relaxation compared with as-grown GaN. A detailed anal- ysis about evolution of the size, density and optical property of GaN hexagonal pyramids is described as a function of light intensity. The intensity of photoluminescence spectra of GaN etched with hexagonal pyramids significantly increases compared to that of as-grown GaN due to multiple scattering events, high quality GaN with pyramids and the Bragg effect. 相似文献
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We characterized the surface defects in a-plane GaN, grown onto r-plane sapphire using a defect-selective etching (DSE) method. The surface morphology of etching pits in a-plane GaN was investigated by using different combination ratios of H3PO4 and H2SO4 etching media. Different local etching rates between smooth and defect-related surfaces caused variation of the etch pits made by a 1:3 ratio of H3PO4/H2SO4 etching solution. Analysis results of surface morphology and composition after etching by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) demonstrated that wet chemical etching conditions could show the differences in surface morphology and chemical bonding on the a-plane GaN surface. The etch pits density (EPD) was determined as 3.1 × 108 cm−2 by atom force microscopy (AFM). 相似文献
6.
T. Akane K. Sugioka K. Midorikawa 《Applied Physics A: Materials Science & Processing》1999,69(7):S309-S313
Photostimulated direct etching of GaN has been demonstrated with extremely high etching rate up to 135 nm/pulse. The process consists of laser irradiation and ex-situhydrochloric acid treatment. Not only deep etching but also a highly planarized surface are obtained by an increase in laser fluence and the number of pulses. Seven-pulse irradiation at 1 J/cm2 decreases surface average roughness (Ra) to ~2 nm from ~10 nm of the untreated sample. No deep-level emission (450-600 nm) is detected in photoluminescence measurement on the samples irradiated with laser fluences as high as 3 J/cm2. 相似文献
7.
Trap states induced by reactive ion etching in AlGaN/GaN high-electron-mobility transistors 下载免费PDF全文
《中国物理 B》2015,(11)
Frequency-dependent conductance measurements were carried out to investigate the trap states induced by reactive ion etching in Al Ga N/Ga N high-electron-mobility transistors(HEMTs) quantitatively. For the non-recessed HEMT, the trap state density decreases from 2.48 × 1013cm-2·e V-1at an energy of 0.29 e V to 2.79 × 1012cm-2·e V-1at E T= 0.33 e V.In contrast, the trap state density of 2.38 × 1013–1.10 × 1014cm-2·e V-1is located at E T in a range of 0.30–0.33 e V for the recessed HEMT. Thus, lots of trap states with shallow energy levels are induced by the gate recess etching. The induced shallow trap states can be changed into deep trap states by 350?C annealing process. As a result, there are two different types of trap sates, fast and slow, in the annealed HEMT. The parameters of the annealed HEMT are E T= 0.29–0.31 e V and D T= 8.16 × 1012–5.58 × 1013cm-2·e V-1for the fast trap states, and E T= 0.37–0.45 e V and D T= 1.84 × 1013–8.50 × 1013cm-2·e V-1for the slow trap states. The gate leakage currents are changed by the etching and following annealing process, and this change can be explained by the analysis of the trap states. 相似文献
8.
An atomic-level controlled etching(ACE)technology is invstigated for the fabrication of recessed gate AlGaN/GaN high-electron-mobility transistors(HEMTs)with high power added efficiency.We compare the recessed gate HEMTs with conventional etching(CE)based chlorine,Cl2-only ACE and BCl3/Cl2ACE,respectively.The mixed radicals of BCl3/Cl2were used as the active reactants in the step of chemical modification.For ensuring precise and controllable etching depth and low etching damage,the kinetic energy of argon ions was accurately controlled.These argon ions were used precisely to remove the chemical modified surface atomic layer.Compared to the HEMTs with CE,the characteristics of devices fabricated by ACE are significantly improved,which benefits from significant reduction of etching damage.For BCl3/Cl2ACE recessed HEMTs,the load pull test at 17 GHz shows a high power added efficiency(PAE)of 59.8%with an output power density of 1.6 W/mm at Vd=10 V,and a peak PAE of 44.8%with an output power density of 3.2 W/mm at Vd=20 V in a continuous-wave mode. 相似文献
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Nonpolar (1120) GaN films are grown on the etched a-plane GaN substrates via metalorganic vapor phase epitaxy. High-resolution X-ray diffraction analysis shows great decreases in the full width at half maximum of the samples grown on etched substrates compared with those of the sample without etching, both on-axis and off-axis, indicating the reduced dislocation densities and improved crystalline quality of these samples. The spatial mapping of the E2 (high) phonon mode demonstrates the smaller line width with a black background in the wing region, which testifies the reduced dislocation densities and enhanced crystalline quality of the epitaxial lateral overgrowth areas. Raman scattering spectra of the E2 (high) peaks exhibit in-plane compressive stress for all the overgrowth samples, and the E2 (high) peaks of samples grown on etched substrates shift toward the lower frequency range, indicating the relaxations of in-plane stress in these GaN films. Furthermore, room temperature photoluminescence measurement demonstrates a significant decrease in the yellow-band emission intensity of a-plane GaN grown on etched templates, which also illustrates the better optical properties of these samples. 相似文献
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The kinetics of defect formation in the system of a crystal with a nonmetal component in the activated gas phase has been
investigated. The data obtained has made it possible to develop physicochemical methods of regulating the defect-formation
processes depending on the adsorption—desorption—crystallization equilibrium on the surface of a crystal. A kinetic model
of defect formation in the AIIBVI and AIIIBV compounds is proposed. Results of the kinetic analysis of the intrinsic defects in the ZnO and GaN compounds are presented.
The photoluminescence spectra of GaN films annealed in a flow of nonmetal-component radicals (atoms) have been considered.
This work was reported at the Vth International Scientific-Technical Conference on Quantum Electronics, November 22–25, 2004,
Minsk, Belarus.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 760–765, November–December, 2005. 相似文献
16.
Marek Włodarczyk 《Optics Communications》1979,31(2):125-128
The details of the fabrication of diffraction gratings in photoresist and GaAs, are reported. Optimum exposures, resulting in uniform, deep gratings in photoresist and GaAs have been found. Also, different etching times have been examined in order to define the best conditions for GaAs grating fabrication. Furthermore, the behaviour of the GaAs grating is shown in comparison with the adequate photoresist mask. 相似文献
17.
Morphology of nonpolar (1120) a-plane GaN epilayers on r-plane (1102) sapphire substrate grown by low-pressure metal-organic vapour deposition was investigated after KOH solution etching. Many micron-and nano-meter columns on the a-plane GaN surface were observed by scanning electron microscopy. An etching mechanism model is proposed to interpret the origin of the peculiar etching morphology. The basal stacking fault in the a-plane GaN plays a very important role in the etching process. 相似文献
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This article reports the properties and the behavior of GaN during the photoelectrochemical etching process using four different electrolytes. The measurements show that the porosity strongly depends on the electrolyte and highly affects the surface morphology of etched samples, which has been revealed by scanning electron microscopy (SEM) images. Peak intensity of the photoluminescence (PL) spectra of the porous GaN samples was observed to be enhanced and strongly depend on the electrolytes. Among the samples, there is a little difference in the peak position indicating that the change of porosity has little influence on the PL peak shift, while it highly affecting the peak intensity. Raman spectra of porous GaN under four different solution exhibit phonon mode E2 (high), A1 (LO), A1 (TO) and E2 (low). There was a red shift in E2 (high) in all samples, indicating a relaxation of stress in the porous GaN surface with respect to the underlying single crystalline epitaxial GaN. Raman and PL intensities were high for samples etched in H2SO4:H2O2 and KOH followed by the samples etched in HF:HNO3 and in HF:C2H5OH. 相似文献
20.
Z. Novotný 《Czechoslovak Journal of Physics》1988,38(3):338-342
Reactive ion etching (RIE) and plasma etching (PE) of different materials (GaAs, Si3N4 SiO2 and photoresist Microposit 1350 H) in freon 116 are compared in the present article. The importance of ion bombardment for the etching rate is evident from the experimental results. GaAs is etched only by RIE due to ion milling, the etching rates of Si3N4 and SiO2 are 4 to 5 times higher by RIE than PE. 相似文献