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A novel noise optimization technique for inductively degenerated CMOS LNA

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Journal of semiconductors 2009年第10期30卷 137-142页

作者：耿志卿王海永吴南健 State Key laboratory for Superlattices and Microstructures Institute of Semiconductors Chinese Academy of Sciences

This paper proposes a novel noise optimization *** technique gives analytical formulae for the noise performance of inductively degenerated CMOS low noise amplifier（LNA）circuits with an ideal gate inductor for a fixed bias voltage and nonideal gate inductor for a fixed power dissipation,respectively,by mathematical analysis and reasonable approximation *** circuits with required noise figure can be designed effectively and rapidly just by using hand calculations of the proposed *** design a 1.8 GHz LNA in a TSMC 0.25 μm CMOS *** measured results show a noise figure of 1.6 dB with a forward gain of 14.4 dB at a power consumption of 5 mW,demonstrating that the designed LNA circuits can achieve low noise figure levels at low power dissipation.

关键词： low noise optimization noise factor

Low-power switched-capacitor delta-sigma modulator for EEG recording applications

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Journal of semiconductors 2010年第7期31卷 121-126页

作者：陈进张旭陈弘达 State Key laboratory of Integrated Optoelectronics Institute of SemiconductorsChinese Academy of Sciences

This paper presents a third-order single-loop delta-sigma modulator of a biomedical micro-system for portable electroencephalogram（EEG） monitoring *** reduce the power consumption,the loop filter of the proposed modulator is implemented by applying a switched-capacitor *** modulator is designed in a 0.35-μm 2P4M standard CMOS process,with an active area of 365×290μm^*** results show that this modulator achieves a 68 dB dynamic range with an input sinusoidal signal of 100 Hz signal bandwidth under a 64 over-sampling *** whole circuit consumes 515μW under a 2.5 V power supply,which is suitable for portable EEG monitoring.

关键词： analog-to-digital converter delta-sigma modulator EEG switched-capacitor circuit

Theoretical study of the optical gain characteristics of a Ge_(1-x)Sn_x alloy for a short-wave infrared laser

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Chinese Physics B 2015年第2期24卷 191-197页

作者：张东亮成步文薛春来张旭丛慧刘智张广泽王启明 State Key laboratory on Integrated Optoelectronics Institute of SemiconductorsChinese Academy of Sciences

Optical gain characteristics of Ge1-xSnμx are simulated *** an injection carrier concentration of 5×10^18/cm^3 at room temperature,the maximal optical gain of Ge0.922Sn0.078 alloy（with n-type doping concentration being 5×10^18/cm^3） reaches 500 cm^-***,considering the free-carrier absorption effect,we find that there is an optimal injection carrier density to achieve a maximal net optical gain.A double heterostructure Ge0.554Si0.289Sn0.157/Ge0.922Sn0.078/Ge0.554Si0.289Sn0.157 short-wave infrared laser diode is designed to achieve a high injection efficiency and low threshold current *** simulation values of the device threshold current density Jth are 6.47 kA/cm^2（temperature：200 K,and λ=2050 nm）,10.75 kA/cm^2（temperature：200 K,and λ=2000 nm）,and23.12 kA/cm^2（temperature：300 K,and λ=2100 nm）,*** results indicate the possibility to obtain a Si-based short-wave infrared Ge1-xSnx laser.

关键词： infrared GeSn alloys semiconductor lasers optoelectronic

NiO removal of Ni/Au Ohmic contact to p-GaN after annealing

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Journal of semiconductors 2009年第2期30卷 101-104页

作者：林孟喆曹青颜廷静张书明陈良惠 Nano-Opto-Electronics laboratory Institute of SemiconductorsChinese Academy of Sciences

The Ni/Au contact was treated with oxalic acid after annealing in 02 ambient, and its 1-V characteristic showed the property of contact has been obviously improved. An Auger electron spectroscopy （AES） depth profile of the contact as-annealed showed that the top layer was highly resistive NiO, while an X-ray photo-electron spectroscopy （XPS） of oxalic acid treated samples indicated that the NiO has been removed effectively. A scanning electron microscope （SEM） was used to observe the surface morphology of the contacts, and it was found that the lacunaris surface right after annealing became quite smooth with lots of small Au exposed areas after oxalic acid treatment. When the test probe or the subsequently deposited Ti/Au was directly in contact with these small Au areas, they worked as low resistive current paths and thus decrease the specific contact resistance.

关键词： oxalic acid treatment specific contact resistance NiO

Photoluminescence Studies of Single Submonolayer InAs Structures Grown on GaAs (001) Matrix

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Chinese Physics Letters 1995年第11期12卷 697-700页

作者： LI Wei WANG Zhanguo LIANG Jiben XU Bo ZHU Zhanping YUAN Zhiliang LI Jian laboratory of Semiconductor Materials Science Institute of SemiconductorsAcademia SinicaBeijing 100083 National Semiconductor Superlattice laboratory Institute of SemiconductorsAcademia SinicaBeijing 100083 National Integrated Optoelectronics laboratory Institute of SemiconductorsAcademia SinicaBeijing 100083

We report a detailed analysis of optical properties of single submonolayer InAs structures grown on GaAs(001)*** is shown that the formation of InAs dots with 1 monolayer(ML)height leads to localization of exciton under certain submonolayer InAs coverage,which play a key role in the highly improved luminescence efficiency of the submonolayer InAs/GaAs structures.

关键词： InAs/GaAs InAs monolayer

Monolithic integration of electroabsorption modulators and tunnel injection distributed feedback lasers using quantum well intermixing

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Chinese Physics B 2010年第12期19卷 328-333页

作者：汪洋潘教青赵玲娟朱洪亮王圩 Key laboratory of Semiconductor Materials Science Institute of SemiconductorsChinese Academy of Sciences

Electroabsorption modulators combining Franz-Keldysh effect and quantum confined Stark effect have been mono-lithically integrated with tunnel-injection quantum-well distributed feedback lasers using a quantum well intermixing method. Superior characteristics such as extinction ratio and temperature insensitivity have been demonstrated at wide temperature ranges.

关键词： electroabsorption modulator tunnel injection wide temperature range operation quantum well intermixing

Design of surface emitting distributed feedback quantum cascade laser with single-lobe far-field pattern and high outcoupling efficiency

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Chinese Physics B 2010年第5期19卷 320-326页

作者：郭万红刘俊岐陆全勇张伟李路王利军刘峰奇王占国 Key laboratory of Semiconductor Materials Science Institute of SemiconductorsChinese Academy of Sciences

A 7.8-μm surface emitting second-order distributed feedback quantum cascade laser （DFB QCL） structure with metallized surface grating is studied. The modal property of this structure is described by utilizing coupled-mode theory where the coupling coefficients are derived from exact Floquet-Bloch solutions of infinite periodic structure. Based on this theory, the influence of waveguide structure and grating topography as well as device length on the laser performance is numerically investigated. The optimized surface emitting second-order DFB QCL structure design exhibits a high surface outcoupling efficiency of 22% and a low threshold gain of 10 cm-1. Using a π phase-shift in the centre of the grating, a high-quality single-lobe far-field radiation pattern is obtained.

关键词： quantum cascade laser Floquet-Bloch expansion distributed feedback lasers surface emission

Formation of rippled surface morphology during Si/Si(100) epitaxy by ultrahigh vacuum chemical vapour deposition

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Chinese Physics B 2011年第12期20卷 328-334页

作者：胡炜玄成步文薛春来苏少坚王启明 State Key laboratory on Integrated Optoelectronics Institute of SemiconductorsChinese Academy of Sciences

The Si epitaxial films are grown on Si （100） substrates using pure Si2H6 as a gas source using ultrahigh vacuum chemical vapour deposition technology. The values of growth temperature Tg are 650 ℃, 700 ℃, 730 ℃, 750 ℃, and 800 ℃. Growth mode changes from island mode to step-flow mode with Tg increasing from 650 ℃ to 700℃. Rippled surface morphologies are observed at Tg = 700 ℃, 730 ℃, and 800℃, but disappear when Tg = 750℃. A model is presented to explain the formation and the disappearance of the ripples by considering the stability of the step-flow growth.

关键词： step-bunching Ehrlich-Chwoebel barrier elastic repulsion fluctuation

What has been measured by reflection magnetic circular dichroism in Ga_(1-x)Mn_xAs/GaAs structures?

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Chinese Physics B 2014年第7期23卷 720-726页

作者：贺振鑫郑厚植黄学骄王海龙赵建华 State Key laboratory of Superlattices and Microstructures Institute of SemiconductorsChinese Academy of Sciences

An explicit expression of reflection magnetic circular dichroism （RMCD） has been derived, taking into account the interference effect that arises from multiple internal reflections in an air/Ga1-xMnxAs/GaAs dielectric layered system. It unambiguously shows that the RMCD signal is composed by three terms. In addition to the conventional term, which is sufficient in the absence of interference, an oscillatory term is required. Both of them are related to the imaginary part εxy of the off-diagonal element of the dielectric tensor. One also becomes aware that in this case RMCD is not actually determined only by the imaginary part εxy of the off-diagonal element of the dielectric tensor, as has been widely accepted. In fact, the real part εxy of the off-diagonal element will substantially mix into the measured RMCD results by another oscillatory cos θ form. It can even reverse the sign of RMCD, when the Gal_xMnxAs layer becomes thicker. The main aspects of these predictions were used to reasonably explain the RMCD results measured in three different types of samples. Our work will bring about a reconsideration of how to correctly explain RMCD results.

关键词： magneto-optical effects magnetic semiconductors optical properties Ⅲ-Ⅴ compounds