沈文忠
固体光谱和光电子器件的应用基础研究
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- 姓名:沈文忠
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学术头衔:
博士生导师
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学科领域:
凝聚态物理学
- 研究兴趣:固体光谱和光电子器件的应用基础研究
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411
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10
沈文忠, Z. Y. Lai, W. Z. Shena)
JOURNAL OF APPLIED PHYSICS, 2003, 94 (1): 367~374,-0001,():
-1年11月30日
Effective mass theory and variation method are used to calculate the ground state energies of excitons in coupled three-quantum dot (3-QD) systems. To calculate multicenter integrals involving two particle wave functions, a series of spheres are used to cover the coordinate space and further approximation has been made when the radii of the integral spheres are suitably selected around the three spherical QDs in near equal radius. The results obtained from the calculation of In0.5Ga0.5As/GaAs and GaAs/Al0.2Ga0.8As coupled 3-QD systems are basically in agreement with the experiments. Based on the energy level schemes in these systems, we make suggestions for the application of far-infrared and/or terahertz sources.
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【期刊论文】Study on the quantum efficiency of resonant cavity enhanced GaAs far-infrared detectors
沈文忠, Y. H. Zhang, H. T. Luo, W. Z. Shena)
JOURNAL OF APPLIED PHYSICS, 2002, 91 (9): 5538~5544,-0001,():
-1年11月30日
We present a detailed theoretical analysis on the quantum efficiency of a resonant cavity enhanced (RCE) GaAs homojunction work function internal photoemission far-infrared (FIR) detector. The quantum efficiency under both resonant and nonresonant conditions has been calculated. All the detector parameters are optimized under the realistically nonresonant condition. The further investigation of the standing wave effect (SWE) shows that the SWE is important and cannot be neglected for the FIR detector. The resulting quantum efficiency is about two times higher than that in the normal GaAs homojunction FIR detector measured by experiment, showing a promising effect. In contrast to the case in the near-infrared region, the wavelength selectivity is not obvious in the FIR region. The theoretical analysis can be applied to other RCE homojunction FIR detectors.
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沈文忠, Y. H. Zhang, H. T. Luo, W. Z. Shena)
APPLIED PHYSICS LETTERS, 2003, 82 (7): 1129~1131,-0001,():
-1年11月30日
A proposal for the bottom mirrors of resonant-cavity-enhanced GaAs homojunction far-infrared (FIR) detectors has been suggested and optimized based on undoped/doped GaAs layers with the Fresnel matrix method. With this kind of bottom mirror, the calculated absorption probability in the detector cavity increases two times over that in the normal detector structure. Comparing optical measurements have been carried out on n-GaAs homojunction FIR detector structures with and without the bottom mirrors, as well as a single optimized bottom mirror structure (without the detector cavity structure). The experimental FIR reflection and transmission results demonstrate well the theoretical design.
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【期刊论文】Bandtail characteristics in InN thin films
沈文忠, W. Z. Shen, L. F. Jiang, H. F. Yang, F. Y. Meng, H. Ogawa, Q. X. Guo
APPLIED PHYSICS LETTERS, 2002, 80 (12): 2063~2065,-0001,():
-1年11月30日
The Urbach bandtail characteristics in InN thin films grown by radio-frequency magnetron sputtering on sapphire (0001) substrates have been investigated both theoretically and experimentally. The bandtail parameter in InN thin films has been obtained by temperature-dependent transmission spectra, with the aid of a detailed calculation of the transmission profile. A bandtail model based on the calculation of density of occupied states and the carrier-phonon interaction has been employed to analyze the temperature-dependent bandtail characteristics. The bandtail parameter is in the range of 90-120meV in the InN thin film. It is found that the carrier-phonon interaction in InN is weak and the structural disorder contribution (~90meV) dominates over the interactive terms. The high structural disorder in InN thin films may relate to the high nonradiative recombination centers.
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【期刊论文】Critical point transitions of wurtzite AIN in the vacuum-ultraviolet spectral range
沈文忠, J. Chen and W. Z. Shena), H. Ogawa, Q. X. Guo
APPLIED PHYSICS LETTERS, 2004, 84 (24): 4866~4868,-0001,():
-1年11月30日
The optical reflection spectra have been measured on a high-quality wurtzite aluminum nitride (AlN) single crystal with synchrotron radiation in the range of 6-16eV at different temperatures. The energy positions of the dominant structures due to the critical point (CP) transitions have been extracted by employing Adachi's dielectric function model. By the aid of the band structure of AIN, we have assigned up to ten CP transitions in the reflection spectra. The crystal-field splitting at the center of the Brilliouin zone is observed to be 110meV. We have further revealed the temperature dependencies of these interband transitions.
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沈文忠, X. Y. Chen and W. Z. Shena)
APPLIED PHYSICS LETTERS, 2004, 85 (2): 287~289,-0001,():
-1年11月30日
We report on the observation of resonant tunneling phenomena due to the electronic transport through zero-and two-dimensional (0D and 2D) states in n-type nanocrystalline silicon snc-Sid/p-type crystalline silicon heterostructures. The transport information of both the 0D and 2D carriers has been extracted by the analysis of magnetic-field-dependent Hall data. Clear 2D-0D steplike and 0D-0D spikelike resonant tunneling structures have been demonstrated up to the high temperature of 220 and 50K in the natural quantum dot system, respectively. The revealed quantum tunneling information should facilitate more practical and more efficient application of nc-Si-based resonant tunneling devices.
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【期刊论文】Long-wavelength optical phonon properties of ternary MgZnO thin films
沈文忠, J. Chen and W. Z. Shena)
APPLIED PHYSICS LETTERS, 2003, 83 (11): 2154~2156,-0001,():
-1年11月30日
Far-infrared (FIR) reflection measurements have been employed to study the long-wavelength optical phonon properties in cubic MgZnO thin films grown by reactive electron beam evaporation on sapphire substrates. The frequencies of the optical phonons with T2 symmetry are obtained by calculating the FIR reflection spectra using a multioscillator model and Kramers–Kronig dispersion analysis. The modified random-element-isodisplacement model has been used to analyze the long-wavelength optical mode behavior in both cubic and hexagonal MgZnO alloys. It is found that cubic MgZnO exhibits a two-mode behavior, while for hexagonal MgZnO, the E1 mode displays a two-mode behavior and the A1 mode a one-mode behavior. The effects of structural transition on the optical phonon frequency, optical mode behavior, and force constant have also been clearly revealed.
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沈文忠, W. Z. Shen
APPLIED PHYSICS LETTERS, 2001, 79 (9): 1285~1287,-0001,():
-1年11月30日
The study of exciton–longitudinal optical (LO) phonon coupling in semiconductor quantum well (QW) structures and their corresponding bulk materials reveals four distinct features: a large difference between (i) III-V and II-VI QW structures, (ii) multiple QW and single QW structures, as well as (iii) QW structures and their corresponding bulk materials, and its linear dependence on well width in QW structures. A quantitatively theoretical approach is presented, which can explain well all the experimental observations and can clarify the controversy in the literature. The effects of alloy disorder and strain in QW structures on exciton-LO phonon coupling are also discussed.
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沈文忠, W. L. Xu, M. J. Zheng, S. Wu, W. Z. Shena)
APPLIED PHYSICS LETTERS, 2004, 85 (19): 4364~4366,-0001,():
-1年11月30日
We report on the structural and optical properties of highly ordered porous alumina membranes (PAMs) under different annealing temperatures up to 1100℃. Clear structural transition from amorphous to γ-and then to a-AI2O3 has been demonstrated in PAMs through x-ray diffraction and micro-Raman scattering measurements. The crystallization of the PAMs under an annealing temperature above 800℃ results in the appearance of two absorption structures in the transmission spectra ranging from 1500 to 1700cm-1 due to the formation of stable carboxylic impurities. We have presented convincing evidence that the blue photoluminescence band in PAMs originates from the coactions of the singly ionized oxygen vacancies (F+ centers) and the luminescent centers transformed from oxalic impurities.
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【期刊论文】Observation of negative thermo-optical coefficient in cubic MgZnO thin films
沈文忠, H. P. Zhou, W. Z. Shena), N. B. Chen, H. Z. Wu
APPLIED PHYSICS LETTERS, 2004, 85 (17): 3723~3725,-0001,():
-1年11月30日
We report on the investigation of thermo-optical coefficient sdn/dTd in cubic MgZnO thin films through temperature-dependent s10–295Kd optical transmission measurements. As a result of potential fluctuation, we observe an anomalous thermal behavior of the band gap in the ternary MgZnO alloy, which limits the observation of negative dn/dT up to 200K. The negative dn/dT is evidenced by the phase shift from the prominent Fabry-Pérot interference fringes and modeled by taking into account the thermal and electronic background contribution, as well as the Wannier exciton effect. It is found that the large thermal expansion in cubic MgZnO plays a key role in the observed negative dn/dT.
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