Delay of the excited state lasing of 1310 nm InAs/GaAs quantum dot lasers by facet coating

In this letter, we present a facet coating design to delay the excited state (ES) lasing for 1310 nm InAs/GaAs quantum dot lasers. The key point of our design is to ensure that the mirror loss of ES is larger than that of the ground state by decreasing the reflectivity of the ES. In the facet coating design, the central wavelength is at 1480 nm, and the high- and low-index materials are Ta2O5 and SiO2, respectively. Compared with the traditional Si/SiO2 facet coating with a central wavelength of 1310 nm, we have found that with the optimal design the turning temperature of the ES lasing has been delayed from 90 to 100 degrees C for the laser diodes with cavity length of 1.2 mm. Furthermore, the characteristic temperature (T-0) of the laser diodes is also improved.

Measurement of w-InN/h-BN Heterojunction Band Offsets by X-Ray Photoemission Spectroscopy

X-ray photoelectron spectroscopy has been used to measure the valence band offset (VBO) of the w-InN/h-BN heterojunction. We find that it is a type-II heterojunction with the VBO being -0.30 +/- A 0.09 eV and the corresponding conduction band offset (CBO) being 4.99 +/- A 0.09 eV. The accurate determination of VBO and CBO is important for designing the w-InN/h-BN-based electronic devices.

Growth and characterization of InAsSb alloys by metalorganic chemical vapour deposition

Low pressure metalorganic chemical vapour deposition (LP-MOCVD) growth and characteristics of InAssb on (100) Gasb substrates are investigated. Mirror-like surfaces with a minimum lattice mismatch are obtained. The samples are studied by photoluminescence spectra, and the output is 3.17 mu m in wavelength. The surface of InAssb epilayer shows that its morphological feature is dependent on buffer layer. With an InAs buffer layer used, the best surface is obtained. The InAssb film shows to be of n-type conduction with an electron concentration of 8.52 x 10(16) cm(-3).

ITO导电玻璃和PDMS微芯片毛细管电泳电化学发光检测的研究

微全分析系统是目前很前沿的研究领域，尽管现在还没有真正意义的微全分析系统出现，但它代表了分析科学的发展趋势。本文主要研究了ITO导电玻璃和PDMS微芯片毛细管电泳和电化学发光检测方法。微芯片毛细管电泳对与其联用的检测器有相当高的要求，一些传统的检测方法很难适应于微芯片毛细管电泳。电化学发光检测是一种新兴的检测技术，在化学、生物、医学诊断以及免疫分析中展现出良好的应用前景。如何实现和完善微芯片毛细管电泳与电化学发光检测联用技术是本论文的重点。我们采用聚二甲基硅氧烷（poly（dimethylsiloxone），简称PDMS）和玻璃作为芯片材料，以锢锡氧化物（indium桩n oXide，简称工T0）导电玻璃为工作电极设计了一种集成化的微芯片毛细管电泳电化学发光检测器。其中，芯片的底片由工TO导电玻璃经光刻、化学腐蚀等方法处理后得到。ITO是一种透明的导电材料，作为工作电极集成到芯片的底片上，PDMS层与芯片底片采用可逆键合的方式键合，大大简化了操作并提高了电化学发光信号的采集效率。我们采用脯氨酸作为被测物对检测器进行了表征。在实验过程中，微芯片毛细管电泳及工T0工作电极都表现出良好的稳定性。我们还提出了电化学和电化学发光同时检测技术，应用于微芯片毛细管电泳和常规毛细管电泳。在这种电化学和电化学发光双检测模式中，三联吡陡钉（Ru（bpy）32+既作为电化学发光检测所需的发光试剂与被分析物反应生成激发态的Ru（bpy）32+＊产生电化学发光信号，又在电极表面平行催化电化学反应得到增强的电流响应，提高电化学检测的灵敏度。电化学信号与电化学发光信号同时产生并分别记录，从而实现了电化学和电化学发光同时检测。我们将这种检测技术与芯片或常规毛细管电泳结合，以多巴胺及三种药物分子山蓖若碱、氧氟沙星和利多卡因作为被测物对其进行了表征。这种同时检测方法与其它多检测模式相比更为简单、方便，比单一的电化学或电化学发光检测可以获得更多的被分析物信息，扩大单一检测方式的应用范围。

Room-Temperature Ferromagnetism in Co-Doped In2O3 Nanocrystals

Co-doped In2O3 nanocrystals showing room-temperature ferromagnetism have been successfully prepared by a simple sol-gel synthesis route. The sample displays it clear ferromagnetism behavior above 300 K. Phase and structure analyses reveal that the nanocrystals are crystallized with Co ions substituted for In ions in the In2O3 matrix, and no trace of secondary phases or clusters is detected. The experimental results are explained theoretically by first-principles calculations based on density functional theory, which indicate that the native ferromagnetic behavior of Co-doped In2O3 could be mainly ascribed to the strong d-d coupling of the magnetic ions.

INFLUENCES OF ALLOY DISORDER AND INTERFACE ROUGHNESS ON OPTICAL-SPECTRA OF INGAAS/GAAS STRAINED-LAYER QUANTUM-WELLS

We present studies of alloy composition and layer thickness dependences of excitonic linewidths in InGaAs/GaAs strained-layer quantum wells grown by MBE, using both photoluminescence and optical absorption. It is observed that linewidths of exciton spectra increase with indium content and well size. Using the virtual crystal approximation, the experimental data are analyzed. The results obtained show that the alloy disorder is the dominant mechanism for line broadening at low temperature. In addition, it is found that the absorption spectra related to light hole transitions have varied from a peak to a step-like structure as temperature increases. This behavior can be understood by the indirect space transitions of light holes.

Study of GSMBE growth and characteristics of high-quality strained In0.63Ga0.37As/InP quantum wells

High-quality compressively strained In0.63Ga0.37As/InP quantum wells with different well widths (1-11 nm) have been grown coherently on InP substrates using a home-made gas source molecular beam epitaxy (GSMBE) system. The indium composition in the wells of the sample was determined by means of high-resolution X-ray diffraction and its computer simulation. it is found that the exciton transition energies determined by photoluminescence (PL) at 10 K are in good agreement with those calculated using a deformation potential model. Sharp and intense peaks for each well can be well resolved in the 10 K PL spectra. For wells narrower than 4 nm, the line width of the PL peaks are smaller than the theoretical values of the line-width broadening due to 1 hit interface fluctuation, showing that the interface fluctuation of our sample is within 1 ML. For wells of 7 and 9 nm, the PL peak widths are as low as 4.5 meV.

Lapping technique of InP single crystal wafer

The wafer processing of Indium Phosphide (InP) is so important that it is getting more and more attentions. Lapping is a basic step just following the ingot cutting. In this paper, the influences of various processing parameters on the lapped wafer quality and lapping rate have been checked, the double-crystal X-ray diffraction results about lapped wafers also were presented here. According to the experimental results, the optimum lapping conditions have been obtained.

Photoluminescence enhancement of (NH4)(2)S-x passivated InP surface by rapid thermal annealing

Photoluminescence enhancement of (NH4)(2)S-x passivated InP surface followed by rapid thermal annealing (RTA) has been investigated by using photoluminescence (PL), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS), An increase in PL intensity of up to 10 times was observed after sulfur passivation and RTA treatment compared to unpassivated InP surface. XPS measurement results show that introduction of RTA process can enhance the sulfur remaining on the passivated surface to bond to indium but no evidence of S-P bond is noticeable. Passivation enhancement mechanism is discussed.

A new structure of In-based ohmic contacts to n-type GaAs

Electrical, structural and reaction characteristics of In-based ohmic contacts to n-GaAs were studied. Attempts were made to form a low-band-gap interfacial phase of InGaAs to reduce the barrier height at the metal/semiconductor junction, thus yielding low-resistance, highly reliable contacts. The contacts were fabricated by e-beam sputtering Ni, NiIn and Ge targets on VPE-grown n(+)-GaAs film (approximate to 1 mu m, 2 x 10(18) cm(-3)) in ultrahigh vacuum as the structure of Ni(200 Angstrom)/NiIn(100 Angstrom)/Ge(40 Angstrom)/n(+)-GaAs/SI-GaAs, followed by rapid thermal annealing at various temperatures (500-900 degrees C). In this structure, a very thin layer of Ge was employed to play the role of heavily doping donors and diffusion limiters between In and the GaAs substrate. Indium was deposited by sputtering NiIn alloy instead of pure In in order to ensure In atoms to be distributed uniformly in the substrate; nickel was chosen to consume the excess indium and form a high-temperature alloy of Ni3In. The lowest specific contact resistivity (rho(c)) of (1.5 +/- 0.5)x 10(-6) cm(2) measured by the Transmission Line Method (TLM) was obtained after annealing at 700 degrees C for 10 s. Auger sputtering depth profile and Transmission Electron Microscopy (TEM) were used to analyze the interfacial microstructure. By correlating the interfacial microstructure to the electronical properties, InxGa1-xAs phases with a large fractional area grown epitaxially on GaAs were found to be essential for reduction of the contact resistance.

PASSIVATION OF THE INP(100) SURFACE USING (NH4)(2)S-X

InP(100) surface treated with (NH4)(2)S-x has been investigated by using photoluminescence(PL), Auger electron spectroscopy and X-ray photoelectron spectroscopy. It is found that PL intensity increased by a factor of 3.3 after (NH4)(2)S-x passivation and the sulfur remained on the surface only bonded to indium, not to phosphorus. This suggests that the sulfur atoms replace the phosphorus atoms on the surface and occupy the phosphorus vacancies.

PHOTOEMISSION-STUDIES OF K-PROMOTED NITRIDATION AND OXIDATION OF THE INP(100) SURFACE USING SYNCHROTRON-RADIATION

The effect of a potassium overlayer on nitridation and oxidation of the InP(100) surface is investigated by core-level and valence-band photoemission spectroscopy using synchrotron radiation. In comparison with the K-promoted nitridation of the InP(110) surface obtained by cleavage in situ, we found that the promotive effect for the InP(100) surface cleaned by ions bombardment is much stronger and that the nitridation products consist of two kinds of complexes: InPNx and InPNx+y. The results confirmed that surface defects play an important part in the promotive effect. Furthermore, in contrast with K-promoted oxidation of InP(100) where bonding is observed between indium and oxygen, indium atoms did not react directly with nitrogen atoms during the K-promoted nitridation of InP(100). (C) 1995 American Vacuum Society.

OPTICAL AND STRUCTURAL-PROPERTIES OF AP-MOVPE GAINP/GAAS HETEROSTRUCTURES

Lattice matched GaInP/GaAs heterostructures were grown by atmospheric pressure-metal organic vapor phase epitaxy (AP-MOVPE). Compositional intermixing of As/P and Ga/In near the heterointerfaces was studied by photoluminescence (PL) spectroscopy. Indium segregation, memory effect of In into GaAs and the carry-over of As in the GaInP layer during the growth process were considered as three major factors giving rise to the anomalous emissions in the PL spectra. Both thermal annealing and zinc doping strongly enhanced the compositional interdiffusion near the heterointerfaces.

PHOTOEMISSION-STUDIES OF K-PROMOTED NITRIDATION OF INP(100) SURFACE USING SYNCHROTRON-RADIATION

The effect of molecular nitrogen exposure on the surfaces of InP(100) modified by potassium overlayers is investigated by core-level and valence-band photoemission spectroscopy using Synchrotron radiation. In comparison with InP(110) surface, we found the promotion is much stronger for InP(100) surface due to the central role of surface defects in the promotion; furthermore, in contrast with K-promoted oxidation of InP(100) where the bonding is observed between indium and oxygen, indium atoms did not react directly with nitrogen atoms during the K-promoted nitridation of InP(100).

Compressively Strained InGaAs/InGaAsP Quantum Well Distributed Feedback Laser at 1.74μm

The compressively strained InGaAs/InGaAsP quantum well distributed feedback laser with ridge-wave- guide is fabricated at 1.74μm. It is grown by low-pressure metal organic chemical vapor deposition（MOCVD）. A strain buffer layer is used to avoid indium segregation. The threshold current of the device uncoated with length of 300μm is 11.5mA. The maximum output power is 14mW at 100mA. A side mode suppression ratio of 35.5dB is obtained.