Photoluminescence up to 1.6 μm of quantum dots with an increased effective thickness of the InAs layer

Multilayered InAs/GaAs quantum dot (QD) heterostructures are produced by metal-organic gas phase epitaxy. The structures exhibit photoluminescence around 1.55 μm at 300 K. The specific feature of the technology is the growth of an InAs layer with an increased effective thickness d _eff to form QDs, in combination with low-temperature overgrowth of the QDs with a thin (6-nm) GaAs layer and with the annelaing of defects. By X-ray diffraction analysis and PL studies, it is shown that, in a structure with the increased thickness d _eff, a secondary wetting InGaAs layer is produced on top of the QD layer from the growing relaxed large-sized InAs clusters on annealing. A new mechanism of formation of large-sized QDs characterized by a large “aspect ratio” is suggested. The mechanism involves the 2D–3D transformation of the secondary InGaAs layer in the field of elastic strains in previously formed QDs. The specific feature of the array of QDs is the coexistence of three populations of different-sized QDs responsible for the multimode photoluminescence in the range from 1 to 1.6 μm. The potentialities of such structures for infrared photoelectric detectors operating in the range from 1–2.5 μm at room temperature are analyzed.     

熔体外延法生长的截止波长12 μm的InAs0.04Sb0.96的电学性质

用Van der Pauw法研究了熔体外延(ME)法生长的截止波长为12 μm的InAs0.04Sb0.96单晶电学性质,测量了其电学性质随温度的变化,结果为300 K时,n＝2.3×1016 cm-3,μ＝6×104 cm2/Vs;200 K时,n＝1×1015 cm-3,μ＝1×105 cm2/Vs.分析了石墨舟和石英舟中生长的外延材料不同的电学特性及其散射机理.结果表明,电离杂质散射控制所有样品在低温时的电子输运过程,而高温时材料的电子迁移率主要由极性光学声子的散射过程决定;C的沾污对石墨舟中生长的InAs0.04Sb0.96单晶在200 K以下的电子迁移率有明显的影响.     

Interband Cascade Lasers with Wavelengths Spanning 2.9 μm to 5.2 μm

We report an experimental investigation of four interband cascade lasers with wavelengths spanning the mid-infrared spectral range, i.e., 2.9 μm to 5.2 μm, near room temperature in pulsed mode. One broad-area device had a pulsed threshold current density of only 3.8 A/cm² at 78 K (λ = 3.6 μm) and 590  A/cm² at 300 K (λ = 4.1 μm). The room-temperature threshold for the shortest-wavelength device (λ = 2.6 μm to 2.9 μm) was even lower, 450 A/cm². A␣cavity-length study of the lasers emitting at 3.6 μm to 4.1 μm yielded an internal loss varying from 7.8 cm⁻¹ at 78 K to 24 cm⁻¹ at 300 K, accompanied by a decrease of the internal efficiency from 77% to 45%.     

Ge基底8～11.5 μm长波通滤光膜的研制

论述了在Ge基底上镀制8～11.5 μm红外长波通滤光膜.通过对Ge基底和Ge、ZnS膜料的色散计算,优化膜系设计,进行工艺实验以及膜层的光学及耐环境实验,制备出满足应用条件的红外长波通滤光片,并已批量生产.     

High-power InAs/InAsSbP heterostructure leds for methane spectroscopy (λ ≈ 3.3 μm)

Two designs of light-emitting diodes (LEDs) based on InAsSbP/InAs/InAsSbP double hetero-structures grown by metal-organic vapor phase epitaxy on p− and n-InAs substrates have been studied. The current-voltage and electroluminescence characteristics of the LEDs are analyzed. It is shown that the LED design with a light-emitting crystal (chip) mounted with the epitaxial layer down on the LED case and emission extracted through the n-InAs substrate provides better heat removal. As a result, the spectral characteristics remain stable at increased injection currents and the quantum efficiency of radiative recombination is higher. The internal quantum efficiency of light-em itting structures with an emission wavelength λ = 3.3–3.4 μm is as high as 22.3%. The optical emission power of the LEDs is 140 μW at a current of 1 A in the quasi-continuous mode and reaches a value of 5.5 mW at a current of 9 A in the pulsed mode.     

Lasing at a wavelength close to 1.3 µm in InAs quantum-dot structures

The feasibility of lasing at a wavelength close to 1.3 μm is demonstrated in InAs quantum-dot structures placed in an external InGaAs/GaAs quantum well. It is shown that the required wavelength can be attained with the proper choice of thickness of the InAs layer deposited to form an array of three-dimensional islands and with a proper choice of mole fraction of InAs in the InGaAs quantum well. Since the gain attained in the ground state is insufficient, lasing is implemented through excited states in the temperature interval from 85 K to 300 K in a structure based on a single layer of quantum dots. The maximum attainable gain in the laser structure can be raised by using three rows of quantum dots, and this configuration, in turn, leads to low-threshold (70 A/cm²) lasing through the ground state at a wavelength of 1.26 μm at room temperature. Fiz. Tekh. Poluprovodn. 33, 1020–1023 (August 1999)     

High performance AlGaN/GaN HEMTs with 2.4 μm source-drain spacing

This paper describes the performance of AlGaN/GaN HEMTs with 2.4 μm source-drain spacing. So far these are the smallest source-drain spacing AlGaN/GaN HEMTs which have been implemented with a domestic wafer and domestic process. This paper also compares their performance with that of 4μm source-drain spacing devices.The former exhibit higher drain current, higher gain, and higher efficiency. It is especially significant that the maximum frequency of oscillation noticeably increased.     

截止波长12μm的InAs0.04Sb0.96/GaAs的熔体外延生长及特性研究

用熔体外延(ME)法在半绝缘(100)GaAs衬底上成功生长出了截止波长为12 μm的InAs0.04Sb0.96外延层.傅立叶变换红外(FTIR)透射光谱揭示,InAsSb合金的禁带宽度被强烈变窄.通过分析InAs0.04Sb0.96外延层载流子浓度的温度依存性表明,其室温禁带宽度为0.105 5 eV,与透射光谱测得的数值很好地一致.通过测量12～300 K的吸收光谱,研究了InAs0.04Sb0.96/GaAs的禁带宽度的温度依存性.霍尔测量得出300 K下样品的电子迁移率为4.47×104 cm2/Vs,载流子浓度为8.77×1015 cm-3;77 K下电子迁移率为2.15×104 cm2/Vs,载流子浓度为1.57×1015 cm-3;245 K下的峰值迁移率为4.80×104 cm2/Vs.     

On the high characteristic temperature of an InAs/GaAs/InGaAsP QD laser with an emission wavelength of ~1.5 μm on an InP substrate

We report on a study of lasers with an emission wavelength of about 1.5 μm and high temperature stability, synthesized on an InP (001) substrate. Self-organized InAs quantum dots capped with a thin GaAs layer are used as the active region of the laser. A quaternary InGaAsP solid solution with a band-gap width of 1.15 eV serves as the waveguide/matrix layer. A high characteristic temperature of the threshold current, T ₀ = 205 K, is reached in the temperature range 20–50°C in ridge-waveguide laser diodes. A correlation between the values of T ₀ and the band-gap width of the waveguide layers is found.     

Quantum-Cascade Ring Resonator Laser with 7–8 μm Wavelength and Surface Radiation Output

Semiconductors - We have created a quantum-cascade laser with 7–8 μm wavelength and surface radiation output through a lattice formed by focused ion beam etching of the upper cladding of...     

Supercontinuum generation at 1.55 μm in an all-normal dispersion photonic crystal fiber with high-repetition-rate picosecond pulses

We demonstrate the generation of supercontinuum（SC） spectrum covering S＋C＋L band of optical communication by injecting 1.4 ps optical pulses with center wavelength of 1552 nm and repetition rate of 10 GHz into an all-normal dispersion photonic crystal fiber（PCF） with length of 80 m. The experimental results are in good agreement with the numerical simulations, which are used to illustrate the SC generation dynamics by self-phase modulation and optical wave breaking（WB）.     

A spatially single-mode laser for a range of 1.25–1.28 μm on the basis of InAs quantum dots on a GaAs substrate

Spatially single-mode lasing in the wavelength range of 1.25–1.28 μm was accomplished in injection lasers on GaAs substrates. The peak output power is 110 mW at room temperature, and the differential quantum efficiency amounts to 37%. The active region of the laser is formed by an array of self-organizing InAs quantum dots. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 34, No. 1, 2000, pp. 117–120. Original Russian Text Copyright ? 2000 by Mikhrin, Zhukov, Kovsh, Maleev, Ustinov, Shernyakov, Kayander, Kondrat’eva, Livshits, Tarasov, Maksimov, Tsatsul’nikov, Ledentsov, Kop’ev, Bimberg, Alferov.     

A 3.1-4.8 GHz transmitter with a high frequency divider in 0.18 μm CMOS for OFDM-UWB

A fully integrated low power RF transmitter for a WiMedia 3.1-4.8 GHz multiband orthogonal frequency division multiplexing ultra-wideband system is presented. With a separate transconductance stage, the quadrature up-conversion modulator achieves high linearity with low supply voltage. The co-design of different resonant frequencies of the modulator and the differential to single (D2S) converter ensures in-band gain flatness. By means of a series inductor peaking technique, the D2S converter obtains 9 dB more gain without extra power consumption. A divided-by-2 divider is used for carrier signal generation. The measurement results show an output power between -10.7 and -3.1 dBm with 7.6 dB control range, an OIP3 up to 12 dBm, a sideband rejection of 35 dBc and a carrier rejection of 30 dBc. The ESD protected chip is fabricated in the Jazz 0.18/zm RF CMOS process with an area of 1.74 mm~2 and only consumes 32 mA current (at 1.8 V) including the test associated parts.     

Effect of total ionizing dose radiation on the 0.25 μm RF PDSOI nMOSFETs with thin gate oxide

Thin gate oxide radio frequency （RF） PDSOI nMOSFETs that are suitable for integration with 0.1μm SO1 CMOS technology are fabricated, and the total ionizing dose radiation responses of the nMOSFETs having four different device structures are characterized and compared for an equivalent gamma dose up to 1 Mrad （Si）, using the front and back gate threshold voltages, off-state leakage, transconductance and output characteristics to assess direct current （DC） performance. Moreover, the frequency response of these devices under total ionizing dose radiation is presented, such as small-signal current gain and maximum available/stable gain. The results indicate that all the RF PDSOI nMOSFETs show significant degradation in both DC and RF characteristics after radiation, in particular to the float body nMOS. By comparison with the gate backside body contact （GBBC） structure and the body tied to source （BTS） contact structure, the low barrier body contact （LBBC） structure is more effective and excellent in the hardness of total ionizing dose radiation although there are some sacrifices in drive current, switching speed and high frequency response.     

1.55 μm InGaAs-InP Quantum Wire Optical Modulators: Optimization of Wire Width to Maximize Absorption and Index of Refraction Changes Due to Excitonic Transitions

Quantum wire/dot modulators offer superior performance over their quantum counterpart due to enhanced excitonic binding energy. This paper presents simulations on InGaAs-InP quantum wire Stark effect optical modulators showing a novel trend. While the excitonic binding energies and absorption coefficients increase as the width of the wire is decreased, the refractive index change Δn is maximized at a wire width depending on the magnitude of the applied electric field. For example, Δn is maximized at a width of about 100Å for an external electric field of 120kV/cm in an InGaAs quantum wire. This behavior is explained by considering the opposing effects of the wire width on binding energy and changes in the electron-hole overlap function in the presence of an external electric field. Practical InGaAs-InP modulators using V-groove structures are also presented.     

MCT infrafed detectors with close to radiatively limited performance at 240 K in the 3–5 µm band

Results are reported on infrared photodiodes which have been designed to minimize the dark diffusion currents for operating temperatures above 200 K in the MWIR (3–5 μm) waveband. It is shown that by adjusting the doping and composition profiles, the dark currents due to Auger and contact diffusion mechanisms can be controlled leading to devices which are close to being radiatively limited. The radiatively-generated current has been calculated as a function of temperature from the measured spectral response and this indicates that the radiative contribution increases from about 53% at 240 K to 65% at 300K. In addition, it is shown that these internally-generated radiative currents can be reduced using negative luminescence. This result is the first experimental verification that the internally-generated radiative mechanism can contribute to the diffusion current.     

Breakdown Voltage and Charge to Breakdown Investigation of Gate Oxide of 0.18μm Dual Gate CMOS Process with Different Measurement Methods

利用击穿电压和击穿电量这两个参数评价标准0.18μm CMOS工艺栅氧的可靠性，获得击穿电压和击穿电量的两个常用方法是电压扫描法和电流扫描法.对用这两种方法得到的击穿电压和击穿电量进行了对比.通过对比，发现测试方法对击穿电压的影响非常小.但是测试方法却可以在很大程度上影响击穿电量.用电流扫描法获得的击穿电量要比用电压扫描法的要大，这一差别可以从两种方法不同的电流-电压曲线中得到解释.同时，通过考察Weibull分布的斜率还发现，击穿电压值的分布斜率要比击穿电量大的多，而且曲线拟合得更好.这说明用击穿电压获得的分析结果更可靠.综合以上结果，可以认为对0.18μm CMOS工艺可靠性评价而言，击穿电压是比较合适的评价指标.     

Tandem small molecule organic photovoltaic cells with broad spectral response up to 1 μm and a high open-circuit voltage

We report a series-connected small molecule tandem photovoltaic cell utilizing two donors with complementary photovoltaic characteristics, lead phthalocyanine (PbPc) in the front subcell and boron subphthalocyanine chloride (SubPc) in the back subcell, to achieve both near infrared (NIR) response up to 1 μm and high open-circuit voltage (V_OC) of more than 1.5 V in the same device. We find that the C₆₀ layer thickness in the front subcell has a critical impact on the overall optical structure and photovoltaic performance of the tandem device. By combining transfer matrix calculations with subcell-selective spectral measurements, we are able to tune the optical field distribution inside the active layers and increase the photocurrent outputs from both subcells, leading to EQE > 30% over the wavelength range 400 nm < λ < 900 nm. This optimized tandem cell exhibits J_SC = (5.5 ± 0.1) mA/cm², fill factor = 0.54, V_OC = 1.53 V, and a power conversion efficiency of (4.5 ± 0.2)%.     

Structure and spectroscopic properties of Er3+/Ce3+ co-doped TeO2-Bi2O3-TiO2 glasses modified with various WO3 contents for 1.53 μm emission

The Er^3＋/Ce^3＋ co-doped tellurite-based glasses （TeO2-Bi2O3-TiO2） modified with various WO3 contents are prepared using conventional melt-quenching technique. The X-ray diffraction （XRD） patterns and Raman spectra of glass sam- ples are measured to investigate the structures. The absorption spectra, the up-conversion emission spectra, the 1.53 /am band fluorescence spectra and the lifetime of Er3＋：4113/2 level are measured, and the amplification quality factors of Er3＋ are calculated to evaluate the effect of WO3 contents on the 1.53 μm band spectroscopic properties. With the in- troduction of WO3, it is found that the prepared tellurite-based glasses maintain the amorphous structure, while the 1.53 μm band fluorescence intensity of Er3＋ is improved evidently, and the fluorescence full width at half maximum （FWHM） is broadened accordingly. In addition, the prepared tellurite-based glass samples have larger bandwidth qual- ity factor than silicate and germanate glasses. The results indicate that the prepared Er3＋/Ce3＋ co-doped tellurite-based glass with a certain amount of WO3 is an excellent gain medium applied for the 1.53 μm band Er3＋-doped fiber ampli- fier （EDFA）.