共查询到20条相似文献,搜索用时 31 毫秒
1.
Pekka Laukkanen Sami Lehkonen Petteri Uusimaa Markus Pessa Anni Seppl Tommy Ahlgren Eero Rauhala 《Journal of Crystal Growth》2001,230(3-4):503-506
We prepared InGaN layers on GaN/sapphire substrates using rf-MBE. Photoluminescence (PL) from these layers, grown at different temperatures TS, shows that there is a strong tendency of GaN to form a separate phase as TS is increased from 600°C to 650°C. Concomitant with the phase separation, the PL from the InGaN phase broadens, which indicates that indium composition in this phase becomes increasingly non-uniform. Indium compositions measured by Rutherford backscattering (RBS) are consistent with these results. We also observed an increase in PL intensity for InGaN layers grown at higher temperatures. In this paper, we also report on preparing a top-contact InGaN/GaN light emitting diode. The device was operated at 447 nm and had the emission line width of 37 nm with no observable impurity related features. The turn-on voltage was 3.0 V. The output power was 20 μW at 60 mA drive current. 相似文献
2.
Control of the morphology of InGaN/GaN quantum wells grown by metalorganic chemical vapor deposition
S. Suihkonen T. Lang O. Svensk J. Sormunen P.T. Trm M. Sopanen H. Lipsanen M.A. Odnoblyudov V.E. Bougrov 《Journal of Crystal Growth》2007,300(2):324-329
Various techniques for morphological evolution of InGaN/GaN multiple quantum well (MQW) structures grown by metalorganic chemical vapor deposition have been evaluated. Atomic force microscopy, photoluminescence (PL) and X-ray diffraction measurements have been used for characterization. It is shown that inclusions, that are generated into the V-defects in the InGaN quantum wells (QW), can be removed by introducing a small amount of hydrogen during the growth of GaN barriers. This hydrogen treatment results in partial loss of indium from the QWs, but smooth surface morphology of the MQW structure and improved optical quality of InGaN wells are obtained. The density of the V-defects could be reduced by reducing the dislocation density of the underlying GaN buffer. 相似文献
3.
Influence of various activation temperatures on the optical degradation of Mg doped InGaN/GaN MQW blue LEDs 总被引:4,自引:0,他引:4
C. J. Youn T. S. Jeong M. S. Han J. W. Yang K. Y. Lim H. W. Yu 《Journal of Crystal Growth》2003,250(3-4):331-338
GaN-based InGaN/GaN multi-quantum-well light emitting diode (MQW LED) structures were grown by metal organic chemical vapor deposition method. The optical properties of the LED structure have been investigated by using the photoluminescence and electroluminescence measurement. Both photoluminescence and electroluminescence results indicate that near pure InN clusters exist within the InGaN layers, which are responsible for the light emission in the LED. With increasing the Mg activation temperature of p-GaN layer, the optical properties of the LED structure tended to significantly degrade. This degradation was found to be deeply related to the variation of InN clusters in the active region. By the current–voltage measurement, a large forward voltage variation was observed. The voltage variation is caused to the conductivity variation of the p-GaN layer due to the different activation temperature. The turn-on voltage obtained from the best LED was 2.56 V and the forward voltage measured at 20 mA was 3.5 V. On the basis of these results, activation of the Mg-doped p-GaN layer must be carried out at the lowest possible value so as to obtain the better performance of LEDs. 相似文献
4.
Keun-Man Song Pil-Geun Kang Heung-Soo Shin Jong-Min Kim Won-Kyu Park Chul-Gi Ko Hyun-Wook Shim Dae Ho Yoon 《Journal of Crystal Growth》2010,312(20):2847-2851
This study examined the influence of strain-compensated triple AlGaN/GaN/InGaN superlattice structures (SLs) in n-GaN on the structural, electrical and optical characteristics of LEDs by analyzing the etch pits density (EPD), stress measurement, high-resolution X-ray diffraction (HRXRD), sheet resistance, photoluminescence (PL) and light–current–voltage (L–I–V). EPD, stress measurement and HRXRD studies showed that the insertion of AlGaN/GaN/InGaN SLs during the growth of n-GaN effectively distributed and compensated for the strong compressive stress, and decreased the dislocation density in n-GaN. The operating voltage at 20 mA for the LEDs grown with SLs decreased to 3.18 V from 3.4 V for the LEDs grown without SLs. In addition, a decrease in the spectral blue shift compared to the LEDs grown without SLs was observed in the LEDs grown with the SLs. 相似文献
5.
Nikhil Sharma David Tricker Paul Thomas Zahia Bougrioua Koen Jacobs Jan Cheyns Ingrid Moerman Ted Thrush Laurence Considine Adam Boyd Colin Humphreys 《Journal of Crystal Growth》2001,230(3-4):438-441
High power LEDs fabricated from InGaN/GaN layers have received much research interest. Hence, in this paper we identify structural and chemical defects resulting from the epitaxial growth of these layers, which directly effect the performance of the device. TEM, annular dark field imaging (ADF), energy filtered TEM (EFTEM) and X-ray mapping were used to study multiple quantum wells structures capped with a p-type GaN layer. TEM and ADF studies of the samples show a number of V-defects which are roughly 100–200 nm apart along the MQW. Each V-defect incorporates a pure edge (
) dislocation, which runs through the apex of the V-defect up to the free surface. These V-defects contain GaN with no InGaN layers, suggesting that the capping layer has filled in the open V-defects. 相似文献
6.
Da-Bing Li Takuya Katsuno Keisuke Nakao Masakazu Aoki Hideto Miyake Kazumasa Hiramatsu 《Journal of Crystal Growth》2006,290(2):374-378
Influence of Si doping on the optical and structural properties of InGaN epilayers with different Si concentrations was investigated in detail by means of high-resolution X-ray diffraction (HRXRD), scanning electron microscope (SEM), Cathodoluminescence (CL) and photoluminescence (PL). It was found that a small amount of Si doping in InGaN could enhance luminescence intensity, improve the crystal quality of InGaN and suppress the formation of V-defects in InGaN. Further investigation by CL showed that V-defects act as nonradiative center, which lower the luminescence efficiency of InGaN. Based on above-mentioned results, one possible mechanism of influence of Si doping on the formation of V-defects in InGaN was also proposed in this paper. 相似文献
7.
A. Hangleiter S. Heppel J. Off B. Kuhn F. Scholz S. Bader B. Hahn V. H rle 《Journal of Crystal Growth》2001,230(3-4):522-526
Using optical gain measurements and calculated optical gain spectra we analyse the various contributions to the threshold current observed for laser diodes. Our model is based on band-to-band transitions and includes internal polarization fields as well as multiple quantum wells. Besides good agreement between experiment and theory, our model explains the characteristic dependence of the threshold current on emission wavelength and well number. 相似文献
8.
Selective-area MOCVD growth for distributed feedback lasers integrated with vertically tapered self-aligned waveguide 总被引:1,自引:0,他引:1
Weibin Qiu Wei Wang Jie Dong Fan Zhou Jingyuan Zhang 《Journal of Crystal Growth》2003,250(3-4):583-587
The growth pressure and mask width dependent thickness enhancement factors of selective-area MOCVD growth were investigated in this article. A high enhancement of 5.8 was obtained at 130 mbar with the mask width of 70 μm. Mismatched InGaAsP (−0.5%) at the maskless region which could ensure the material at butt-joint region to be matched to InP was successively grown by controlling the composition and mismatch modulation in the selective-area growth. The upper optical confinement layer and the butt-coupled tapered thickness waveguide were regrown simultaneously in separated confined heterostructure 1.55 μm distributed feedback laser, which not only offered the separated optimization of the active region and the integrated spotsize converter, but also reduced the difficulty of the butt-joint selective regrowth. A narrow beam of 9° and 12° in the vertical and horizontal directions, a low threshold current of 6.5 mA was fabricated by using this technique. 相似文献
9.
InGaN height-controlled quantum dots (HCQDs) were grown by alternately depositing In0.4Ga0.6N QD and In0.1Ga0.9N spacer layers on a seed In0.4Ga0.6N QD layer. Structural and optical studies showed that the height of the InGaN QDs was controlled by the deposition cycle of In0.4Ga0.6N/In0.1Ga0.9N layers. Photoluminescence studies showed that the In0.4Ga0.6N HCQDs provided deep potential wells and the piezoelectric field-induced quantum-confined Stark effect was negligibly small. These phenomena are attributed to variation in quantum confinement energy in the electronically coupled InGaN HCQDs providing deep potential wells. 相似文献
10.
NaCl:(F2+)AH-type color center laser crystals were prepared by the crystal growth, additional coloration, annealing, and by light aggregation at 290 and 77 K. The formation process of color center in NaCl crystals were investigated, the influence of doped cation and anion ions on the stability and optical properties of color centers is discussed in this paper. 相似文献
11.
Wei Li Jani Turpeinen Petri Melanen Pekka Savolainen Petteri Uusimaa Markus Pessa 《Journal of Crystal Growth》2001,230(3-4):533-536
Strain-compensated GaInNAs/GaAsP quantum well structures and lasers were grown by gas source molecular beam epitaxy using a RF-plasma nitrogen radical beam source. The optimal growth condition for the quantum well structure was determined based on room-temperature photoluminescence measurements. Effects of rapid thermal annealing (RTA) on the optical properties of GaInNAs/GaAsP quantum well structures as well as laser diodes are examined. It was found to significantly increase the photoluminescence from the quantum wells and reduce the threshold current density of the lasers, due to a removal of N induced nonradiative centers from GaInNAs wells. 相似文献
12.
Nola Li Shen-Jie Wang Eun-Hyun Park Zhe Chuan Feng Hung-Lin Tsai Jer-Ren Yang Ian Ferguson 《Journal of Crystal Growth》2009,311(22):4628-4631
Sapphire and SiC are typical substrates used for GaN growth. However, they are non-native substrates and result in highly defective materials. The use of ZnO substrates can result in perfect lattice-matched conditions for 22% indium InGaN layers, which have been found to suppress phase separation compared to the same growths on sapphire. InGaN layers were grown on standard (0 0 0 2) GaN template/sapphire and (0 0 0 1) ZnO substrates by metalorganic chemical vapor deposition. These two substrates exhibited two distinct states of strain relaxation, which have direct effects on phase separation. InGaN with 32% indium exhibited phase separation when grown on sapphire. Sapphire samples were compared with corresponding growths on ZnO, which showed no evidence of phase separation with indium content as high as 43%. Additional studies in Si-doping of InGaN films also strongly induced phase separation in the films on sapphire compared with those on ZnO. High-resolution transmission electron microscopy results showed perfectly matched crystals at the GaN buffer/ZnO interface. This implied that InGaN with high indium content may stay completely strained on a thin GaN buffer. This method of lattice matching InGaN on ZnO offers a new approach to grow efficient emitters. 相似文献
13.
D. J. As T. Frey M. Bartels K. Lischka R. Goldhahn S. Shokhovets A. Tabata J. R. L. Fernandez J. R. Leite 《Journal of Crystal Growth》2001,230(3-4):421-425
Cubic AlyGa1−yN/GaN heterostructures on GaAs(0 0 1) substrates were grown by radio-frequency plasma-assisted molecular beam epitaxy. High resolution X-ray diffraction, micro-Raman, spectroscopic ellipsometry, and cathodoluminescence measurements were used to characterize the structural, optical and vibrational properties of the AlyGa1−yN epilayers. The AlN mole fraction y of the alloy was varied between 0.07<y<0.20. X-ray diffraction reciprocal space maps demonstrate the good crystal quality of the cubic AlyGa1−yN films. The measured Raman shift of the phonon modes of the AlyGa1−yN alloy was in excellent agreement with theoretical calculations. Both SE and CL of the AlyGa1−yN epilayer showed a linear increase of the band gap with increasing Al-content. 相似文献
14.
J. L. Pau E. Monroy E. Muoz F. B. Naranjo F. Calle M. A. Snchez-García E. Calleja 《Journal of Crystal Growth》2001,230(3-4):544-548
The fabrication and characterisation of AlxGa1−xN (0x0.35) photodetectors grown on Si(1 1 1) by molecular beam epitaxy are described. For low Al contents (<10%), photoconductors show high responsivities (10A/W), a non-linear dependence on optical power and persistent photoconductivity (PPC). For higher Al contents the PPC decreases and the photocurrent becomes linear with optical power. Schottky photodiodes present zero-bias responsivities from 12 to 5 mA/W (x=0−0.35), a UV/visible contrast higher than 103, and a time response of 20 ns, in the same order of magnitude as for devices on sapphire substrate. GaN-based p–n ultraviolet photodiodes on Si(1 1 1) are reported for the first time. 相似文献
15.
D. Cherns H. Mokhtari C. G. Jiao R. Averbeck H. Riechert 《Journal of Crystal Growth》2001,230(3-4):410-414
Electron holography in a field emission gun transmission electron microscope has been used to profile the inner potential V0 across GaN/x nm In0.1Ga0.9N/GaN/(0 0 0 1) sapphire samples (x=10, 40 nm) grown by molecular beam epitaxy and viewed in cross-section. Results are presented which suggest a decrease in V0 of 3–4 V across the InGaN layer in the [0 0 0 1] direction. It is proposed that the results can be explained by charge accumulation across the InGaN layer and that the opposing contributions due to piezoelectric and polarisation fields are effectively masked by Fermi level pinning. 相似文献
16.
Y. Cordier J.-C. Moreno N. Baron E. Frayssinet J.-M. Chauveau M. Nemoz S. Chenot B. Damilano F. Semond 《Journal of Crystal Growth》2010,312(19):2683-2688
The growth of GaN based structures on Si(1 1 0) substrates by molecular beam epitaxy using ammonia as the nitrogen precursor is reported. The structural, optical and electrical properties of such structures are assessed and are quite similar to the ones obtained on Si(1 1 1) in-spite of the very different substrate surface symmetry. A threading dislocation density of 3.7×109 cm−2 is evaluated by transmission electron microscopy, which is in the low range of typical densities obtained on up to 2 μm thick GaN structures grown on Si(1 1 1). To assess the potential of such structure for device realization, AlGaN/GaN high electron mobility transistor and InGaN/GaN light emitting diode heterostructures were grown and their properties are compared with the ones obtained on Si(1 1 1). 相似文献
17.
Growth of good quality InGaN multiple quantum wells by MOCVD 总被引:1,自引:0,他引:1
Annamraju Kasi Viswanath J. I. Lee S. T. Kim Dongho Kim 《Journal of Crystal Growth》2004,260(3-4):322-326
We report the optical properties of the blue emitting LED material that belongs to the III–V nitrides family. Quantum wells of InGaN were grown by metal organic chemical vapor deposition. Sapphire was used as the substrate material. Continuous wave and time resolved luminescence experiments were conducted in the temperature range of liquid helium to room temperature. Very intense blue luminescence was observed upto the room temperature. From the very broad linewidth of the emission it was concluded that the compositional fluctuations were dominant. At very low temperatures the lifetimes were found to be somewhat longer than the free exciton case which indicated the localization of excitons at potential fluctuations in the InGaN lattice. 相似文献
18.
Bo Hyun Kong Hyung Koun Cho Mi Yang Kim Rak Jun Choi Bae Kyun Kim 《Journal of Crystal Growth》2010,312(14):2128-2132
InGaN/GaN multiple quantum well-based blue light emitting diodes (LEDs) with different spacer layer structures were grown by metalorganic chemical vapor deposition. Fast-Fourier-transformed high-resolution transmission electron microscopy was used to determine the influence of the strain status in the spacer layer on Mg distribution and device performance. A comparison of the (1 1¯ 0 0) planar distance showed that the high-temperature grown InGaN layer in the spacer had a high level of stored strain. This led to the formation of a continuous facet contrast induced by Mg segregation in the p-layer, which was responsible for the deterioration of the electroluminescence performance of the LEDs. These results show that the delicate control of stored strain in nitride films is important for improving the device performance. 相似文献
19.
Transmission electron microscopy (TEM), cathodoluminescence in the scanning electron microscope (SEM-CL) and photoluminescence (PL) studies were performed on a 30 nm GaN/2 nm In0.28Ga 0.72N/2 μm GaN/(0 0 0 1) sapphire single quantum well (SQW) sample. SEM-CL was performed at low temperatures ≈8 K, and at an optimum accelerating voltage, around 4–6 kV to maximise the quantum well (QW) luminescence. The CL in the vicinity of characteristic “V-shaped” pits was investigated. The near band edge (BE) luminescence maps from the GaN showed bright rings inside the boundaries of the pits while the QW luminescence maps showed pits to be regions of low intensity. These observations are consistent with TEM observations showing the absence of QW material in the pits. Variations in both the BE and QW maps in the regions between the pits are ascribed to threading edge dislocations. The CL and PL QW luminescence was observed to blue-shift and broaden with increasing excitation intensity. This was accompanied by decreasing spatial resolution in the CL QW maps implying an increasing carrier diffusion length in the InGaN layer. The reasons for this behaviour are discussed. It is argued that screening of the piezoelectric field in the material may account for these observations. 相似文献
20.
M. F. Lazarescu D. Pantelica A. S. Manea R. V. Ghita F. Negoita 《Journal of Crystal Growth》2002,240(3-4):401-406
We found Oxygen-doped GaAs crystals to be suitable materials for CO2 laser optical component preparation, with application at 10.6 μm. An optical transmission of 55% in the IR spectrum range, between 2 and 15 μm has been reached for such a GaAs type material. The GaAs crystals that we have analysed were grown by two procedures: Horizontal Bridgman (HB) and Liquid Encapsulated Czochralski (LEC). The HB method has been used for obtaining pure (undoped) crystals, while the oxygen-doped GaAs ingots were grown by LEC technique. The two types of samples processed in the same manner as regards mechanical polishing and chemical etching, which were investigated by Hall measurements, optical transmission spectrometry and elastic recoil detection analysis (ERDA) technique. The GaAs:O (LEC) has near semi-insulating properties as can be observed from the results of the electrical resistivity and Hall effect measurements. The ERDA spectrum shows an intense signal of oxygen in the bulk of GaAs:O (LEC) crystals, while the oxygen signal is not present in the ERDA spectrum of the undoped GaAs (HB). We consider that these results could recommend the ERDA technique as a possible qualitative and quantitative analysis in an ion-beam accelerator for oxygen content in oxygen-doped GaAs crystals. The analysis is not sensitive to the native oxide, as could be seen by measuring GaAs (HB) undoped crystals. 相似文献