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。     

Double quantum wire GaAs/AlGaAs diode lasers grown byorganometallic chemical vapor deposition on grooved substrates

Structure and lasing characteristics of double-quantum-wire lasers are reported. Threshold current as low as 2.4 mA and continuous wave operation at room temperature were achieved for lasers with uncoated facets. Subbands due to lateral quantum confinement were observed in the laser spectra. Good agreement between measured dependence of threshold current on cavity length and a simple model accounting for gain saturation was found     

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。     

Intervalley scattering in GaAs/AlGaAs quantum wells and quantum cascade lasers

The results of simulations of Γ−X scattering in GaAs/AlGaAs quantum wells are presented, discussing the importance of the mole fraction, doping density, and lattice and electron temperatures in determining the scattering rates. A systematic study of Γ−X scattering in GaAs/Al_xGa_1−xAs heterostructures, using a single quantum well to determine the importance of well width, molar concentration x, lattice temperature, and doping density, has been performed. After this we consider a double quantum well to determine the role of intervalley scattering in the transport through single-layer heterostructures, i.e. Γ−X−Γ scattering compared with Γ−Γ scattering. Finally, we estimate the relative importance of intervalley scattering in a GaAs-based quantum-cascade laser device and compare it with other relevant scattering mechanisms important to describe carrier dynamics in the structure. Our simulations suggest that Γ−X scattering can be significant at room temperature but falls off rapidly at lower temperatures.     

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。     

GaAs/AlGaAs环形激光器的量子阱结构优化

为了研究量子阱结构对半导体环形激光器阈值电流的影响,从F-P腔激光器的振荡条件出发,分析了半导体环形激光器的阈值电流密度与量子阱结构参量的函数关系,并推导出最佳量子阱数的表达式。利用器件仿真软件ATLAS建立环形激光器的等效模型,仿真、分析了不同工作温度下,量子阱数、阱厚及势垒厚度对阈值电流的影响。结果表明,阈值电流随量子阱数和阱厚的增加先减小后增大,存在一组最佳值;在确定合适的量子阱数和阱厚后,相对较窄的势垒厚度有助于进一步降低阈值电流;采用GaAs/AlGaAs材料体系和器件结构,其最佳量子阱结构参量为M=3,dw=20nm及db=10nm。     

AlGaAs/GaAs emitter-down HBT fabricated by MBE overgrowth

A planar emitter-down AlGaAs/GaAs heterojunction bipolar transistor (HBT) has been fabricated by a molecular beam epitaxy overgrowth of the n-GaAs collector on top of the base layer after the base layer was formed by beryllium implantation and rapid thermal annealing. The emitter down transistors fabricated by this process had DC current gains of 20, and ring oscillators gave a maximum switching speed of 250 ps/gate.<>     

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.     

Electron mobility in a AlGaAs/GaAs/AlGaAs quantum well

An oscillatory dependence of the electron mobility on the quantum well (QW) thickness in a AlGaAs/GaAs/AlGaAs heterostructure with double-sided modulation doping has been observed experimentally. A steep decrease in mobility with increasing electron concentration in the QW is established. The conditions for an increase in mobility on introducing a thin barrier into the QW are determined. The first experimental observation of an increase in mobility by a factor of 1.3 in a QW of thickness L=26 nm upon introducing a thin (1–1.5 nm) AlAs barrier is reported.     

单模GaAs/AlGaAs短腔长量子级联激光器

通过缩短Fabry-Pérot腔量子级联激光器的腔长,得到了激射波长为11.4μm的单模GaAs/AlGaAs量子级联激光器。纵模间距与F-P腔腔长成反比,腔长为150μm的器件实现了稳定单模激射,在85K时边模抑制比达到19dB。     

Single-mode GaAs/AlGaAs quantum cascade microlasers

Single-mode edge emitting GaAs/A1GaAs quantum cascade microlasers at a wavelength of about 11.4 μm were realized by shortening the Fabry-P6rot cavity length. The spacing of the longitudinal resonator modes is inversely proportional to the cavity length. Stable single-mode emission with a side mode suppression ratio of about 19 dB at 85 K for a 150-μm-long device was demonstrated.     

Self-consistent rate equations of self-assembly quantum wire lasers

We describe a detailed model for the dynamical and spectral properties of quantum dash (quantum wire assembly) lasers. We use a self-consistent semiclassical theory for a multimode laser field which interacts with an inhomogeneously broadened assembly of quantum wires via the quantum mechanical radiation-matter interaction. Our comprehensive coupled equations are spectrally resolved enabling to study accurately the effect of the gain inhomogeneity. Carrier-carrier and carrier-phonon scattering are also included. We highlight the effective capture rate which is determined by the ratio between the number of states in the reservoir and in the assembly, the energetic region into which carriers are captured and the width of the inhomogeneously broadened gain. Specifically, we demonstrate that a large number of states ratio lowers both the linear optical differential gain and the nonlinear gain coefficient. We show that gain suppression dominates when a realistic energy range into which capture takes place is considered as well as for small number of states ratios. In addition, we show that the width of the inhomogeneous broadening plays a relatively small role. We conclude that the differential gain and nonlinear damping can not be optimized simultaneously. These results point therefore to the clear advantages offered by laser structures which employ non conventional carrier injection schemes such as tunnelling barrier or n-type /spl delta/-doping regions.     

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。     

Planar AlGaAs/GaAs HBT fabricated by MOCVD overgrowth with a grownbase

A planar heterojunction bipolar transistor (HBT) with an AlGaAs emitter layer epitaxially grown onto a selectively defined grown base layer, where the base is grown with the collector as part of the original epi, is discussed. The transistors fabricated with this process exhibit good gain and output characteristics. Transistors with 7×7 μm² emitters have exhibited a DC current gain of 10 to 1000 for base doping from 1×10¹⁹ to 8×10¹⁷ cm³, respectively, and Early voltages ⩾100 V. The propagation delay of 19-stage ring oscillators was 87 ps/gate. The transistor-fabrication process was designed to be manufacturable, and the planar nature of the transistor surface should permit large-scale integration with good yields     

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     

Birefringence of disordered AlGaAs/GaAs quantum wells

Birefringence at room temperature is analysed for interdiffusion induced (disordered) Al/sub 0.3/Ga/sub 0.7/As/GaAs single quantum well structures in the wavelength range 0.5 mu m to 1.0 mu m. The confinement profile for the disordered QW is modelled by an error function and the refractive index model includes excitonic effects and contributions from the Gamma , X and L Brillouin zones. Results show that at longer wavelengths the birefringence is small and varies from positive to negative before reducing to zero as interdiffusion proceeds. For wavelengths between the QW and barrier band-edges, the birefringence is large and reduces with increasing interdiffusion.<>     

Transverse junction stripe lasers using Si-doped GaAs/AlGaAs grown by MBE

Transverse junction stripe (TJS) laser diodes on a semi-insulating substrate have been fabricated using Si-doped GaAs/AlGaAs double-heterostructure layers grown by MBE. Room-temperature CW operation of the TJS laser with a low threshold current (30 mA) has been achieved.     

Ion beam milling-induced damage in AlGaAs/GaAs/AlGaAs single quantum well

Ion beam milling-induced damage in a 500 AA AlGaAs/40 AA GaAs/500 AA AlGaAs single quantum well structure was investigated using low temperature cathodoluminescence spectroscopy. The ion beam energy (500-1500 eV) dependence of luminescence intensity indicated that minimum damage is introduced at a beam energy of 500 eV. Most (80-85%) of the original luminescence intensity was recovered on annealing at 400 degrees C for 5 min.<>     

AlGaAs/GaAs 2-DEG FET's fabricated from MO-CVD Wafers

A transconductance (gm) of as high as 330 mS/mm is obtained from wafers grown by MO-CVD in which triethyl gallium and triethyl aluminum are used as organometallic compounds. A comparison between the experimental and theoretical results is made for the dependence of gmon the thickness of the AlGaAs layer. The saturation of velocity of 2-DEG determined from the drain I-V characteristics is found to be as high as 2 × 10⁷cm/s regardless of the absence of the undoped spacer layer.