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     

单量子阱GaAs/AlGaAs半导体激光器

本文介绍了用分子束外延法制作的梯度折射率分别限制式单量子阱GaAs/AlGaAs半导体激光器。该器件具有较低的阈值电流密度和单模运转特性,连续输出功率可达55mw。     

AlGaAs/InGaAs/GaAs quantum-well power MISFET at millimeter-wavefrequencies

An AlGaAs/InGaAs/GaAs quantum-well MISFET developed for power operation at millimeter-wave frequencies is described. The InGaAs channel is heavily doped to increase the sheet carrier density, resulting in a maximum current density of 700 mA/mm with a transconductance of 480 mS/mm. The 0.25-μm×50-μm device delivers a power density of 0.76 W/mm with 3.6-dB gain and 19% power-added efficiency at 60 GHz. At 5.2 dB gain, the power density is 0.55 W/mm. A similar device built on an undoped InGaAs channel had much poorer power performance and no speed advantage     

20 dB contrast GaAs/AlGaAs multiple quantum-well nonresonantmodulators

The authors report a successful fabrication of nonresonant GaAs/AlGaAs multiple quantum well (MQW) modulators with a contrast ratio of more than 20 dB and a wide bandwidth of 3 nm. The optical path, as long as 8 μm, is attained by fabricating a high-purity thick MQW layer with a residual carrier concentration of less than 10¹⁴ cm^-3 and introducing a high-reflectivity AlAs/AlGaAs quarter-wavelength mirror. The driving wavelengths are located at the absorption edge, resulting in the low-absorption loss     

Photoelectrical memory in GaAs/AlGaAs multilayer quantum-well structures

An increase in the dark current (by 2–3 orders of magnitude) in GaAs/Al_xGa_1−x As multilayer quantum-well structures with x⋍0.4 is observed after illumination of the structures with optical light (λ<1.3 μm). This increase is sustained for an extended time (more than 10³ s) at low temperatures. It then decreases to its initial value upon heating of the sample. A model of the barrier with local sag of the conduction band facilitating tunneling is proposed. The conduction band sag and the magnitude of the current grow due to optical ionization of uncontrolled deep level clusters present in the barrier and decrease due to subsequent capture of electrons from the conduction band by the deep levels upon heating. Fiz. Tekh. Poluprovodn. 32, 209–214 (February 1998)     

Effect of GaAs/AlGaAs quantum-well structure on refractive index

We investigate the refractive index difference between the GaAs/AlGaAs quantum wells (QWs) and bulk AlGaAs. We find the refractive index difference is smaller when the electric field in the nominally intrinsic MQW region is larger, or when the well (GaAs) thickness of the QW's is larger, or when the Al fraction of the QWs is smaller. The maximum refractive index difference between the 100 Å GaAs/100 Å Al_0.2Ga_0.8As QWs at zero electric filed and bulk Al_0.1Ga_0.9As is about 0.044. Even with a small refractive index difference of 0.0132, the OFF-state reflectance of a normally-off MQW modulator at the designed photon wavelength will increase from the desired value of 0% to 90% when the reflectivity of the bottom mirror is 0.99     

Vertical integration of a GaAs/AlGaAs quantum-well laser and along-wavelength quantum-well infra-red photodetector

A short-wavelength (~0.8 μm) GaAs/AlGaAs graded-index separate-confinement heterostructure quantum-well laser has been monolithically integrated with a long-wavelength (~8 μm) GaAs/AlGaAs multiple-quantum-well infra-red photodetector on a semi-insulating GaAs substrate by molecular beam epitaxy. The vertical integration method is used and the combined structure is a pinin structure. Both the laser and detector exhibit excellent characteristics. At room temperature, the ridge waveguide laser has an extremely low threshold current of 25 mA and a differential quantum efficiency above 65% with a stripe width of 20 μm. The quantum-well detector has a peak response at 8 μm and a responsivity of 0.7 A/W     

单模AlGaAs／GaAs脊形波导量子阱半导体激光器

本文报道用分子束外延设备研制梯度折射率分别限制式单量子阱AlGaAs/GaAs脊形波导半导体激光器。该激光器具有良好的性能,条宽5μm器件室温阈值电流23mA,线性连续输出单模激光功率大于15mW。     

Gain suppression in GaAs/AlGaAs TJS lasers

Experimental results on gain suppression in transverse junetion stripe (TJS) lasers with a heavily doped active region is reported for the first time. These lasers oscillate in the fundamental transverse and lateral modes with gain suppression, and reproducibly operate in a single-longitudinal mode up to 1.8 times the threshold current.     

Ridge waveguide AlGaAs/GaAs distributed feedback lasers

Ridge waveguide AlGaAs/GaAs distributed feedback lasers were fabricated by a two-step molecular beam epitaxy. A threshold current as low as 37 mA, which is the lowest ever reported, was obtained under a continuous wave condition at room temperature. The low threshold current is due to the larger coupling coefficient (91 cm^-1) and a good current and optical confinement. The effects of the facet coatings were investigated and a high-power and a high-temperature operation was obtained. The polarization and the dynamic behavior were also investigated.     

Functional AlGaAs/GaAs heterostructure-emitter bipolar transistor with a pseudomorphic InGaAs/GaAs quantum-well base

A new functional AlGaAs/GaAs heterostructure-emitter bipolar transistor (HEBT) with a pseudomorphic InGaAs/GaAs quantum-well (QW) base structure is presented. Due to the insertion of an InGaAs QW between the emitter–base (E–B) junction, the valence band discontinuity can be enhanced. The excellent transistor characteristics including a high current gain of 280 and a low offset voltage of 100 mV are obtained. In addition, an interesting multiple S-shaped negative differential resistance (NDR) phenomenon is observed under the inverted operation mode. This may be attributed to an avalanche multiplication and sequential two-stage barrier lowering effect.     

Temperature dependence of GaAs/AlGaAs multiquantum barrier lasers

A GaAs/AlGaAs laser loaded by a multiquantum barrier (MQB) is reported, and its temperature-threshold characteristic has been systematically examined. It has been found that this characteristic is improved by introducing the MQB, and this improvement is reflected in the barrier height. The actual barrier heights of a MQB-loaded structure under biased conditions are also discussed, considering the Fermi level in the MQB region     

AlGaAs/GaAs双异质结激光器退化的研究

观察了室温下工作的DH激光器退化现象,发现在短时间内退化的器件,除阈值升高外尚伴随着微分量子效率下降。对热稳定性良好,并对于较长时间(>250小时)阈值上升率(△J_(th)/J_(th)千小时)小于3％的器件,高温老化证明它们的寿命都能超过万小时量级。     

Characteristics of AlGaAs/GaAs quantum-well delta-doped channel FET(QUADFET)

The transport properties of a two-dimensional electron gas in Al _0.3Ga_0.7As/GaAs quantum-well delta-doped heterostructures are studied. Electron energy subbands in the quantum well were calculated by a self-consistent method. The FETs having a gate length of 1.3 μm showed a transconductance as high as 340 mS/mm. The FETs also showed a broad plateau of transconductance around its peak, which is not typical in MODFETs     

Record power characteristics of InGaAs/AlGaAs/GaAs heterostructure lasers

Continuous-wave output powers of 9.2 W at a constant heatsink temperature of 10°C and 12.2 W at a stabilized temperature of the active region have been obtained on an InGaAs/AlGaAs laser with a 0.4-μm-thick waveguide, operating at 1.03 μm. Record-breaking output mirror power densities of, respectively, 29.9 and 40 MW/cm² have been achieved without catastrophic optical mirror damage in the two temperature-stabilization regimes. A maximum power conversion efficiency of 66% has been achieved in a laser with a cavity length of 2 mm. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 35, No. 3, 2001, pp. 380–384. Original Russian Text Copyright ? 2001 by Livshits, Egorov, Kochnev, Kapitonov, Lantratov, Ledentsov, Nalyot, Tarasov. Deceased.     

GaAs/AlGaAs太赫兹量子级联激光器的热分析

为研究太赫兹量子级联激光器(THz QCLs)中的热传输及有效散热方法,建立了二维/三维有限元热分析模型,模拟计算了GaAs/AlGaAs THz QCLs低温工作时的温度及热流分布;并讨论了源区结构参数、热沉材料及散热膜层对器件热传输的影响规律。研究结果表明,器件源区温度水平方向分布较均匀,垂直方向温差大,源区热量主要依靠热沉导出;减小源区厚度、增加腔长与减小脊宽均有利于促进热传导并降低源区温度;在器件顶部增加AlN薄膜具有显著的辅助散热效果,当薄膜厚度大于8 μm时,源区温降趋于缓慢。     

Very low threshold current ridge-waveguide AlGaAs/GaAs single-quantum-well lasers

Ridged-waveguide AlGaAs/GaAs single-quantum-well lasers were fabricated from a molecular-beam-grown GRIN-SCH wafer in which a superlattice buffer layer was introduced. Fabricated diodes exhibited excellent lasing characteristics including a very low threshold current of 5 mA with a T0 value as high as 160 K.     

GaAs/AlGaAs grating surface-emitting diode lasers on Si substrates

A monolithic grating surface-emitting, GaAs/AlGaAs, separate-confinement-heterostructure, single-quantum-well diode laser has been fabricated on a Si substrate using a single-step metalorganic chemical vapour deposition process. An output power of 30 mW has been obtained under pulsed operation with a peak emission wavelength of 885 nm.<>     

Improving performance of AlGaAs/GaAs monolithic laser/FET by GRIN-SCH quantum-well laser

An AlGaAs/GaAs graded-index-waveguide separate-confinement-heterostructure (GRIN-SCH) single-quantum-well (SQW) laser has been monolithically integrated with a couple of field-effect-transistor drivers on a semi-insulating GaAs substrate. The adoption of the GRIN-SCH SQW laser has enabled an improvement in the laser/FET performance, exhibiting a low laser threshold current (12 mA) and a high sensitivity of the output light power to the input gate voltage (7.5 mW/facet/V).     

On the temperature delocalization of carriers in GaAs/AlGaAs/InGaAs quantum-well heterostructures

The effect of temperature delocalization in semiconductor lasers (emission wavelength λ = 1060 nm) based on symmetric and asymmetric separate-confinement heterostructures fabricated by metal-organic vapor-phase epitaxy (MOVPE) is studied. Experimental and calculated estimates show that the carrier concentration in the waveguide increases by an order of magnitude when the temperature of a semiconductor laser is raised by ～100°C. It is found that an increase in the temperature of the active zone leads to enhancement of the temperature delocalization of both electrons and holes. It is shown that the delocalization of holes begins at higher temperatures, compared with that of electrons. It is demonstrated experimentally that the onset of temperature delocalization depends on the threshold carrier concentration in the active region of a laser at room temperature. It is found that raising the energy depth of the active region by choosing the waveguide material makes it possible to fully suppress the temperature-delocalization process up to 175°C.