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1.
We report a fabrication approach in which we combine self-assembled metal/molecule nanostructures with chemically stable semiconductor surface layers. The resulting structures have well controlled dimensions and geometries (∼4 nm Au nanoclusters) provided by the chemical self-assembly and have stable, low-resistance interfaces realized by the chemically stable semiconductor cap layer (low-temperature grown GaAs passivated by the organic tether molecules). Scanning tunneling microscope imaging and current-voltage spectroscopy of nanocontacts ton-GaAs fabricated using this approach indicate high quality, ohmic nanocontacts having a specific contact resistance of ∼1 × 10−7Ω·cm2 and a maximum current density of ∼1×107 A/cm2, both comparable to those observed in large area contacts. Uniform 2-D arrays of these nanocontact structures have been fabricated and characterized as potential cells for nanoelectronic device applications.  相似文献   

2.
CuInTe2 and CuInSe2 are direct bandgap ternary chalcopyrite (I-III-VI2) semiconductors which are the simplest ternary analogs of the II-VI zincblende compounds. Some of the chalcopyrites exhibit nonlinear optical properties which make them good candidates for optical device technology. We have done preliminary studies on the influence of Mn2+ on the optical, transport and magnetic properties of CuInTe2 in analog to previous stud-ies of Mn:CdTe etc. Bulk polycrystalline p-type samples, with up to 12% Mn substi-tution, have been examined with polarized light microscopy, x-ray energy dispersive analysis, optical spectrometry, van der Pauw technique and SQuID magnetometer mea-surements. From the metallurgical studies, Mn is found to substitute for Cu but not In. The bandgap of Mn:CuInTe2 is larger than 0.92 eV. Most of our samples show phonon limited mobility, with the highest mobility occurring at ≈75K. Without Mn substitu-tion, CuInTe2(Se2) is diamagnetic. Samples with 3% Mn substitution in Cu sites are paramagnetic. At higher Mn concentration (3% < x < 12%), the (Cu1-xMnx)InTe2 sam-ples show antiferromagnetic coupling and a measured effective magnetic moment up to ≈5.4 μB/Mn atom. Samples with attempted Mn substitution in In sites (from 3% to 9%) show anomalous magnetic behavior at low temperatures.  相似文献   

3.
Electron-optical techniques were employed to fabricate planar silicon transistors having a 1-micron strip width and a combined dimensional and registration tolerance of 1000 Å. A new electron-sensitive positive resist was used to define a conventional oxide diffusion mask. The exposure equipment is described and electrical parameters of the complete device are given.  相似文献   

4.
Nanocrystal (NC) based non-volatile memories are a leading candidate to replace conventional floating gate memory. Substituting the poly-silicon gate with a layer of discrete nanocrystals or nanodots provides increased immunity to charge loss. Metallic nanocrystals have been found to be advantageous over Si- or Ge-based approaches due to good controllability of the size distribution and the achievable NC densities as well as increased charge storage capacity of metallic nanocrystals. Sufficiently high NC densities have been achieved to demonstrate feasibility for sub-32 nm node non-volatile memory devices.  相似文献   

5.
The Bloch function analysis is applied to the problem of periodical phase-locked semiconductor laser array structures. This method makes it possible to treat in the same manner both evanescent and leaky modes of such structures and to optimize these structures in order to get maximum content in the central lobe of emission far-field pattern. If one places high gain in the low-index array regions, the preferred array modes are leaky modes coupled either in-phase or out-of-phase depending on parameters of structure. The linear and nonlinear problems of the propagation of finite aperture beams in such laser structures are considered. Propagation of such a beam is described by the Schrodinger equation with `photon mass' determined by a curvature of photon dispersion  相似文献   

6.
采用密度泛函理论(DFT)框架下的局域密度近似(LDA),计算了四方HfO2晶体的电子结构,包括能带结构和态密度.在此基础上计算了四方Hf02晶体的光学线性响应函数,包括复介电函数、吸收光谱、复折射率和光电导谱.通过比较发现,计算结果与实验结果吻合较好,说明采用密度泛函理论的局域密度近似来计算HfO2材料的光学性质是比较可靠的.  相似文献   

7.
A theoretical analysis of spontaneous emission from a quantum well in dielectric multilayer structures, especially the influence of dielectric geometry on the relative intensities of guided and radiation modes and on polarization, is presented. We first discuss a relatively simple three-layer case, and subsequently a technologically more interesting five-layer structure that has been proposed for a high-power laser. The expression for the partial as well as total, emission rates is derived within a broader framework of coupled Heisenberg equations of motion for charge carriers and the quantized electromagnetic field. Thereby, the explicit mode decomposition of the Green tensor is avoided. Still, the beta factor for individual guided modes, which is a relevant quantity for the lasing threshold of a device, can be identified and a competition between modes is shown to exist in specific cases  相似文献   

8.
Burt  M.G. Taylor  R.I. 《Electronics letters》1985,21(17):733-734
The ratio of the spontaneous emission and Auger recombination rates for quantum wells and wires is compared theoretically with that for bulk structures. Dramatic improvements in radiative efficiency are not predicted for these novel structures unless carrier densities are greatly reduced.  相似文献   

9.
A theoretical demonstration of optical bistability in periodic layered media, particularly in long-period GaAs/AlAs superlattices is presented. The proposed structure consists of a periodic multilayer system, as opposed to previously demonstrated nonlinear bistable devices which employed Fabry-Perot etalons. The optical resonance effect which is essential for bistable devices is, in this case, induced by a refractive index modulation. The nonlinear active medium is distributed in the whole structure rather than placed between the two mirrors of a Fabry-Perot cavity. It is shown by a complete calculation of wave propagation in the periodic nonlinear medium that a multiple valued feature appears in the structure's nonlinear reflectivity spectrum. The input/output characteristics of the structure exhibit bistable hysteresis similar to that of a nonlinear Fabry-Perot etalon  相似文献   

10.
A theoretical analysis is made of the intensity distribution within a Kossel line from a semiconductor crystal in an extremely asymmetric x-ray diffraction scheme. Crystals of thickness comparable with the x-ray penetration depth are evaluated as a potential means of bringing about the anomalous Kossel effect, which is predicted to occur in the vicinity of a degenerate point. The possibility is investigated of using a thin amorphous film to enhance the effect. Dispersion-surface geometry, excitation points, and Poynting-vector directions are examined in detail for the anomalous Kossel effect.  相似文献   

11.
Self-heating effects in basic semiconductor structures   总被引:2,自引:0,他引:2  
Investigates the effects of self-heating on the high current I -V characteristics of semiconductor structures using a fully coupled electrothermal device simulator. It is shown that the breakdown in both resistors and diodes is caused by conductivity modulation due to minority carrier generation. In isothermal simulations with T=300 K, avalanche generation is the source of minority carriers. In simulations with self-heating, both avalanche and thermal generation of minority carriers can contribute to the breakdown mechanism. The voltage and current at breakdown are dependent on the structure of the device and the doping concentration in the region with lower doping. For all structures, except highly doped resistors with poor heating sinking at the contacts, the temperature at thermal breakdown ranged from 1.25Ti to 3Ti , where Ti is the temperature at which the semiconductor goes intrinsic. Hence, it is found that T=Ti is not a general condition for thermal (or second) breakdown. From these studies, an improved condition for thermal breakdown is proposed  相似文献   

12.
Boundary conditions (BCs) to the Poisson and transport equations for stationary transport processes of non-equilibrium carriers in semiconductor structures are formulated. The applicability of the resulting BCs for several materials (metals, bipolar semiconductors, including ones in the quasineutrality approach, QNA) and their structures are analyzed for both closed and open circuits. As a first step, general BCs for different types of contacts between two materials and between a solid and the vacuum under thermodynamic equilibrium conditions are thoroughly discussed. Later on, BCs are presented for the general case of a contact between a solid (this contact is considered as a “free-surface” in a broad sense) and the vacuum under non-equilibrium conditions. The concept of “free-surface”, and its BCs, can be extended and applied to other interfaces such as semiconductor–insulator that is relevant in semiconductor devices. Finally, the case of a hetero-contact between two conducting media under a current flow is addressed. BCs for closed-circuit conditions are presented and it is shown that BCs for open-circuit can be obtained as a limit of the proposed ones when the electric current tends to zero. In all the considered cases the changes operated in the BCs if the QNA is invoked are carefully studied.  相似文献   

13.
《Microelectronics Journal》2003,34(5-8):379-382
Self-assembled quantum dots and wires were obtained in the InxGa1-xAs/GaAs and InAs/In0.52Al0.48As/InP systems, respectively, using molecular beam epitaxy (MBE). Uniformity in the distribution, density, and spatial ordering of the nanostructures can be controlled to some extent by adjusting and optimizing the MBE growth parameters. In addition, some interesting observation on the InAs wire alignment on InP(001) is discussed.  相似文献   

14.
采用第一性原理平面波赝势方法,分析了ZnS及掺杂Er3+之后的电子结构,进而预测了其光学性质。结果表明,掺杂之后体系的带隙变窄,同时价带与导带之间形成一个新的中间带。随着掺杂Er3+浓度的增加,体系的绝缘性呈下降趋势,吸收光谱则发生红移现象。这一结论与前人报道的实验结果相符。  相似文献   

15.
The advances in lasers, electronic and photonic integrated circuits (EPIC), optical interconnects as well as the modulation techniques allow the present day society to embrace the convenience of broadband, high speed internet and mobile network connectivity. However, the steep increase in energy demand and bandwidth requirement calls for further innovation in ultra-compact EPIC technologies. In the optical domain, advancement in the laser technologies beyond the current quantum well (Qwell) based laser technologies are already taking place and presenting very promising results. Homogeneously grown quantum dot (Qdot) lasers and optical amplifiers, can serve in the future energy saving information and communication technologies (ICT) as the work-horse for transmitting and amplifying information through optical fiber. The encouraging results in the zero-dimensional (0D) structures emitting at 980 nm, in the form of vertical cavity surface emitting laser (VCSEL), are already operational at low threshold current density and capable of 40 Gbps error-free transmission at 108 fJ/bit. Subsequent achievements for lasers and amplifiers operating in the O-, C-, L-, U-bands, and beyond will eventually lay the foundation for green ICT. On the hand, the inhomogeneously grown quasi 0D quantum dash (Qdash) lasers are brilliant solutions for potential broadband connectivity in server farms or access network. A single broadband Qdash laser operating in the stimulated emission mode can replace tens of discrete narrow-band lasers in dense wavelength division multiplexing (DWDM) transmission thereby further saving energy, cost and footprint. We herein reviewed the1 progress of both Qdots and Qdash devices, based on the InAs/InGaAlAs/InP and InAs/InGaAsP/InP material systems, from the angles of growth and device performance. In particular, we discussed the progress in lasers, semiconductor optical amplifiers (SOA), mode locked lasers, and superluminescent diodes, which are the building blocks of EPIC and ICT. Alternatively, these optical sources are potential candidates for other multi-disciplinary field applications.  相似文献   

16.
We theoretically investigated the lattice structure, interface bonding energy, optical absorption properties and electronic properties of WZ-ZnO (1 1 2)/CdS (1 1 0) interface from first-principles calculations. The interface lattice mismatch is less than 4.3%. The atomic bond lengths and atomic positions change slightly on the interface after relaxation. The WZ-ZnO (1 1 2)/CdS (1 1 0) interface has bonding energy about −0.61 J/m2, suggesting that this interface can exist stably. Through analysis of the density of states, no interface state is found near the Fermi level. In addition, there are orbital hybridizations between different interfacial atoms, and these orbital hybridizations effectively enhance the bonding of Zn and S atoms, Cd and O atoms on the interface. By analysis of difference density charge and Bader charge, we find that electrons on the interface are largely redistributed and charges transport near the Fermi level which strengthen the adhesion of the interface.  相似文献   

17.
The interaction between radiation and matter is very important in the study of materials used in the aerospace industry. The improvement of the resistance of various devices is crucial. In the present work we have produced simulation results of damages induced in electronic devices of III–V semiconductor compounds, using SRIM-TRIM, CASINO and GEANT4 programs. The energies used for + particles, SRIM-TRIM, were from 500 keV to 4 MeV for both FETs and HEMTs and the energies used for β particles, CASINO, were from 1 to 500 keV.  相似文献   

18.
郝跃  张金风  沈波  刘新宇 《半导体学报》2012,33(8):081001-8
近年来,氮化物半导体电子器件和材料研究有了重大的进展。在国家自然科学基金资助下,西安电子科技大学、北京大学和中科院微电子所完成了国家自然科学基金重点项目《GaN宽禁带微电子材料和器件重大基础问题研究》。致力于通过氮化物电子材料和器件的基础物理机理研究提高GaN电子材料的结晶质量和电学性能、发展新结构GaN异质结材料研究,获得高性能的GaN HEMT微波功率器件。本文主要介绍该项目在GaN微波功率HEMT和新型高k栅介质MOS-HEMT、InAlN/GaN材料的生长和物性缺陷分析以及HEMT器件研制、GaN异质结的量子输运和自旋性质研究以及GaN材料高场输运性质和耿氏器件等几个方面取得的研究进展。  相似文献   

19.
Negative electronic feedback (EFB) has a strong effect on the performance of a bistable laser diode amplifier and on injection-locked lasers. Negative EFB drastically reduces the switching-up input power level and the hysteresis in the input-output power characteristic and in the tuning curves of the bistable laser amplifier. Furthermore, negative EFB leads to a reduction in the time delay associated with optical switching in diode laser amplifiers. This provides a means of enhancing the versatility of the proposed system in some potential applications. For an injected-locked laser, negative EFB achieves a broadening in the locking bandwidth and its dynamically stable region  相似文献   

20.
Based on the results of a large-signal computer simulation, a trapped plasma mode of oscillation is described in an n+-n-n+ silicon structure. The mechanism is similar to TRAPATT in many ways, but relies upon space-charge injection of majority carriers rather than a depletion region for the necessary initial electric field profile. A necessary design criteria ofN_{d}L < 10^{12}cm-2is established.  相似文献   

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