Highly coherent long cavity GaAs/AlGaAs single quantum-well lasers

Measurements of the spectral properties of ridge waveguide graded index separate-confinement heterostructure single-quantum-well GaAs/AlGaAs lasers are discussed. Long cavity lasers (800 μm) exhibit remarkably pure single-longitudinal mode spectra under continuous operation in spite of the short cavity mode spacing. At an output power of 5 mW, the sidemode suppression exceeds 24 dB and the linewidth is 1.5 MHz. The linewidth-power product is 6.4 MHz-mW. Measurements of the linewidth power product as a function of cavity length L gives an L^-2 dependence in agreement with theory for lasers with small internal loss. The results are used to deduce the linewidth enhancement factor α at the gain peak wavelength ant its dependence on the excitation level. A decrease in α was observed for lasers operating at the second quantized state due to a recovery of the differential gain     

High-power lasers (γ = 808 nm) based on the AlGaAs/GaAs heterostructures of separate confinement

Semiconductors - Laser diodes with a wavelength of 808 nm obtained by the MOC-hydride epitaxy in a system of the AlGaAs alloys have been studied. Parameters of the laser diodes with symmetric...     

Optoelectronic integrated four-channel transmitter arrayincorporating AlGaAs/GaAs quantum-well lasers

A four-channel optoelectronic integrated transmitter array which is fabricated on a single GaAs substrate and operates at 834 nm is described. Each of the circuits incorporates a laser, a photodiode for laser power monitoring, and a laser driver circuit consisting of three GaAs field-effect transistors and a resistor. Laser threshold current of 15-21 mA, transmitter conversion efficiency of approximately 6 mW/V and high-speed operation at a bit rate of more than 1.5-Gb/s NRZ with allowable crosstalk have been demonstrated. A preliminary aging test of the lasers indicated that their stability is comparable to that of discrete devices. The results have demonstrated the feasibility of applying the transmitter array to optical components that process multichannel optical signals at high speed     

High-power highly strained InGaAs quantum-well lasers operating at1.2 μm

High-power highly strained In_xGa_1-xAs quantum-well lasers operating at 1.2 μm are demonstrated. The edge emitting broad area (BA) laser diode structures are grown by metal organic vapor phase epitaxy at low growth temperatures using trimethylgallium, trimethylindium, and arsine sources. In the laser structure, an InGaAs QW is sandwiched between the GaAs waveguide and AlGaAs cladding layers. The operating wavelength for the laser diode at room temperature (20°C) is about 1206 nm, which redshifts to 1219 nm at 46°C. The transparency current density for the BA laser diodes is as low as 52 A/cm² and the characteristic temperature value is 76 K. High-power laser operation in the pulse mode (about 1.6 W) at room temperature was achieved     

1.2 nm capacitance equivalent thickness gate stacks on Si-passivated GaAs

Experiments to increase the specific capacitance of MOS capacitors consisting of HfO₂ on a passivating interfacial layer (IL) of amorphous Si (a-Si) on GaAs are described. XPS analysis of the layers and electrical measurements on the capacitors are combined to study the evolution of the gate stack during deposition and subsequent heat treatments. It is shown that oxidation of the a-Si IL is a major factor in preventing the attainment of a scaled capacitance equivalent thickness (CET). By controlling the deposition of the layers, the gate metal and the heat treatments, a highly scaled gate stack with a CET of 1.2 nm and a leakage reduction of more than 4 orders of magnitude with respect to SiO₂/Si was realized.     

Observation of bistability in GaAs quantum-well vertical-cavitysurface-emitting lasers

Two different types of bistability in proton-implanted GaAs quantum-well (QW) vertical-cavity surface-emitting lasers (VCSELs) have been observed. The first type of bistability has a small hysteresis width (~50 μA) in the light versus current and voltage versus current characteristics. Light-induced large negative differential resistance, random fluctuations, and self-pulsations are observed at the switching point. The emission patterns show that the bistability occurs at a spatially localized area under the output facet that covers only a small fraction of the N1S-μm-diameter aperture. The bistability stems from spatially localized saturable absorption. The second type of bistability has a large hysteresis width (~1 μA) in the L-1 characteristics and is observed well above the threshold current. In this case, no observable bistable loop exists in the voltage versus current characteristics, and the bistability is associated with transverse mode-hopping     

High-power single-mode operation in DFB and FP lasers usingdiffused quantum-well structure

Distributed feedback (DFB) and Fabry-Perot (FP) semiconductor lasers with step and periodic interdiffusion quantum-well structures are proposed for high-power single-longitudinal-mode operation. It is shown that the phase-adjustment region formed by the diffusion step (i.e., step change in optical gain and refractive index) counteracts the influence of spatial hole burning, especially for DFB lasers with large coupling-length products biased at high injection current. Furthermore, it is found that with careful design of the diffusion grating (i.e., grating period and amount of diffusion extent) of FP lasers, side-mode suppression ratio can be enhanced and threshold current density can be minimized to a satisfied level     

High-power InAlGaAs/GaAs and AlGaAs/GaAs semiconductor laser arrays emitting at 808 nm

Molecular beam epitaxy (MBE) growth, device fabrication, and reliable operation of high-power InAlGaAs/GaAs and GaAlAs/GaAs laser arrays are described. Both InAlGaAs/GaAs and AlGaAs/GaAs laser arrays reached maximum continuous wave output powers of 40 W at room temperature. The external quantum efficiency was 50% and 45% for the InAlGaAs/GaAs and AlGaAs/GaAs laser arrays, respectively. Threshold current density for InAlGaAs/GaAs and AlGaAs/GaAs lasers was 303 A/cm/sup 2/ and 379 A/cm/sup 2/, respectively. While the current of AlGaAs laser arrays went up significantly after 1000 h of operation at a constant power of 40 W, InAlGaAs laser arrays had an increase in the injection current of less than 4% after 3000 h at 40 W.     

A 0.5 V 320 MHz 8 bit×8 bit pipelined multiplier in 130 nm CMOS process

This paper presents an 8×8 bit pipelined multiplier operating at 320 MHz under 0.5 V supply voltage. Using PMOS forward body bias technique, the modified full adder and the new D flip-flop with synchronous output are combined and implemented in the proposed pipelined multiplier to achieve high operation speed at supply voltages as low as 0.5 V. The proposed pipelined multiplier is fabricated in 130 nm CMOS process. It operates up to 320 MHz and the power consumption is only 1.48 mW at 0.5 V. Moreover, the power consumption of the proposed pipelined multiplier at 0.5 V is reduced over 5.7 times than that of the traditional architecture at 1.2 V. Thus, the proposed 8×8 bit pipelined multiplier is suitable for SoC and dynamic voltage frequency scaling applications.     

A 6.9 mA 5 bits 90 nm 1 GS/s ADC without calibration for UWB application

Power consumption of high-speed low-resolution ADCs can be reduced by means of calibration. However, this solution presents some drawbacks like allocating a calibration time, calibration algorithm complexity, calibration circuit implementation, etc. In alternative, this paper presents a 5-bit 1 Gs/s ADC without calibration, realized in a 90 nm-CMOS. The device is based on the use of an improved version of double tail dynamic comparators, operating with a fixed bias current. These comparators present a reduced kickback noise, allowing increasing the input transistors sizes in order to improve the matching. The ADC current consumption is equal to 6.9 mA from a 1.2 V supply.     

808 nm高功率AlGaAs/GaAs单量子阱远结激光器

设计并研制了一种将p-n结和有源层分开的高功率AlGaAs/GaAs单量子阱远异质结(SQW-RJH)激光器,其发射波长为808 nm,腔长为900 μm,条宽为100μm.其外延结构与通常的808 nm AlGaAs/GaAs单量子阱半导体激光器的结构不同,在p-n结和有源区间多了一层0.3μm厚的p型Al0.3Ga0.7As下波导层.对研制的器件进行了电导数测试,结果显示,与常规AlGaAs/GaAs大功率半导体激光器相比,远结半导体激光器具有阚值电流偏大、导通电压偏高的直流特性.经4 200h的恒流电老化结果表明,器件在老化初期表现出阈值电流随老化时间缓慢下降,输出功率随老化时间缓慢上升的远结特性.     

780 nm band TM-mode laser operation of GaAsP/AlGaAs tensile-strained quantum-well lasers

Tensile-strained active layer GaAs/AlGaAs separate-confinement-heterostructure quantum-well lasers are reported. These lasers oscillate in the 780 nm band in the TM mode by TM mode gain enhancement in the tensile-strained active layer. The threshold current density of single-quantum-well laser diodes increases rapidly with heatsink temperature. However, triple-quantum-well laser diodes with a cavity length of 485-110 mu m oscillated with a threshold current density of 1.4 and 3.0 kA/cm/sup 2/.<>     

980nm InGaAs／GaAs／AlGaAs大功率LDs模式特性研究

针对目前大功率980 nm量子阱半导体激光器(LDs)为降低阈值电流而要求激射条宽窄、腐蚀深度深而造成的P-I曲线扭折、侧向模式不稳定问题采用有效折射率近似方法进行模拟分析,并得到了实验上的证实.通过采用不对称波导及双量子阱结构,制备了低阈值(19 mA)模式稳定的InGaAs/GaAs/AlGaAs LDs,其斜率效率0.6 W/A(8 μm×500 μm,未镀膜器件),在输出功率达到100 mW时保持横模、侧模的稳定.     

850 nm wavelength range nanoscale resonant optical filter fabrication using standard microelectronics techniques

The fabrication and characterization of a nanoscale resonant optical filter at wavelength around 850 nm is reported using standard C-MOS compatible microelectronics techniques. We discuss the different steps of the process and their impact on the final structure. We show that the use of these techniques gives an efficient filter on glass substrate with high transmission and a narrow bandwidth of 0.4 nm. We also demonstrate the same process on a silicon substrate for a potential integration with electronic functions.     

Self longitudinal-mode stabilisation in GaAs/(AlGa)As quantum-well lasers

Single-longitudinal-mode operation of zero-order lateral mode quantum-well GaAs/(AlGa)As Fabry-Perot lasers has been found to occur over a very wide operating current range. Single-longitudinal-mode operation is very stable, typically allowing an increase in optical output power from 0 to >20mW/facet before mode-hopping occurs. The mode hop at ~23mW leads to bistable single-longitudinal-mode operation with a very large hysteresis loop.     

GaInNAsSb/GaAs vertical cavity surface emitting lasers at 1534 nm

Electrically pumped, C-band vertical cavity surface emitting lasers (VCSELs) grown on GaAs are reported for the first time. The VCSELs employed three GaInNAsSb quantum wells separated by GaNAs barriers. Pulsed lasing was observed at 1534 nm, in the ITU C-band, when cooled. These lasers exhibit the longest wavelength reported to date for electrically pumped VCSELs grown on GaAs substrates.     

32 nm node BEOL integration with an extreme low-k porous SiOCH dielectric k = 2.3

A 32 nm node BEOL integration scheme is presented with 100 nm metal pitch at local and intermediate levels and 50 nm via size through a M1-Via1-M2 via chain demonstrator. To meet the 32 nm RC performance specifications, extreme low-k (ELK) porous SiOCH k = 2.3 is introduced at line and via level using a Trench First Hard Mask dual damascene architecture. Parametrical results show functional via chains and good line resistance. Integration validation of ELK porous SiOCH k = 2.3 is investigated using a multi-level metallization test vehicle in a 45 nm mature generation.     

High-power 0.98-μm strained quantum-well lasers fabricated usingin situ monitored reactive ion beam etching

0.98-μm wavelength InGaAs-AlGaAs strained quantum-well buried ridge lasers were fabricated using in situ monitored reactive ion beam etching (RIBE). This technique allowed a very accurate ridge geometry, resulting in high single transverse-mode power more than 250 mW and high-fiber coupled power more than 150 mW     

Failure analysis of InGaAs/GaAs strained-Layer quantum-well lasers using a digital OBIC monitor

The mechanisms that cause the sudden failure of InGaAs/GaAs strained-layer quantum-well lasers (LD) are analyzed by monitoring an optical beam-induced current (OBIC). Statistically, the LDs that suddenly fail have different n-OBIC/sub ridge/ intensity profiles (p-n junction OBIC under the ridge normalized by that under the electrode) from LDs with conventional catastrophic optical damage. It appears that dislocations are generated in the vicinity of an antireflection (AR) facet and extend to the AR facet, and meltdown finally occurs there. The suppression of dislocation generation around the AR facet is important in regards to preventing sudden failure.     

Photomodulated transmittance of GaBiAs layers grown on (0 0 1) and (3 1 1)B GaAs substrates

In this work, photomodulated transmittance (PT) has been applied to investigate the energy gap of GaBiAs layers grown on (0 0 1) and (3 1 1)B GaAs substrates. In PT spectra, a clear resonance has been observed below the GaAs edge. This resonance has been attributed to the energy gap-related absorption in GaBiAs. The energy and broadening of PT resonances have been determined using a standard approach in electromodulation spectroscopy. It has been found that the crystallographic orientation of GaAs substrate influences on the incorporation of Bi atoms into GaAs and quality of GaBiAs layers. The Bi-related energy gap reduction has been determined to be ∼90 meV per percent of Bi. In addition to PT spectra, common transmittance spectra have been measured and the energy gap of GaBiAs has been determined from the square of the absorption coefficient α² around the band-gap edge. It has been found that the tail of density of states is significant for GaBiAs and influences the accuracy of energy gap determination from the α² plot. In the case of PT spectra, the energy gap is determined unambiguously since this technique is directly sensitive to singularities in the density of states.