Strain effects in (AlyGa1-y)xIn1-xP lasers operating at fixed threshold gain

The authors have studied the effects of strain in AlGaInP quantum well lasers of a fixed well width of 65 Å in which the threshold gain remains approximately constant as the amount of strain is varied. The intrinsic threshold current is found to decrease monotonically as both tensile and compressive strain is applied     

Electronic band structures and optical gain spectra of strainedwurtzite GaN-AlxGa1-xN quantum-well lasers

The electronic band structures, density-of-states, and optical gain spectra for wurtzite GaN-Al_xGa_1-xN quantum wells are studied theoretically based on the Hamiltonian derived using the k.p method. We investigate the dependence of the optical gain and transparent current density on the well width, barrier height, and strain using a numerical approach with high accuracy. The mole fraction of Al in the barrier material is progressively increased to study the effects of quantum confinement and compressive strain. A higher Al mole fraction in the barrier leads to improvement of the TE optical gain and suppression of the TM optical gain. Furthermore, we demonstrate that a reduction of the well width offers improved modal gain over all radiative current densities. We also predict a transparent current density of 250 A/cm² for the GaN-Al_xGa_1-x N single quantum-well (QW) structure. Our results suggest that a suitable combination of thin well width and large barrier height should be selected in improving the TE optical gain in wurtzite GaN-Al_x Ga_1-xN single QW     

Strained layer InxGa1-xAs/GaAs and InxGa1-xAs/InyGa1-yPmultiple-quantum-well optical modulators grown by gas-source MBE

The first results on low-power p-i-n diode modulator structures using strained multiple quantum wells (MQW's) of InGaAs/InGaP grown by gas-source molecular beam epitaxy (MBE) on GaAs are presented. A comparison of transmission, reflection, and photocurrent spectra for these nonresonant devices with those fabricated from InGaAs/GaAs indicates larger modulation, with a maximum change in reflection of >42% observed at 5-V bias at a wavelength of 0.96 μm     

InxGa1-xAs-AlyGa1-yAs-GaAs strained-layer quantum-well heterostructure circular ringlasers

The growth, processing, and optical characterization of a single Y-junction In_xGa_1-xAs-Al_yGa_1-y As-GaAs strained-layer quantum-well heterostructure circular ring laser (6 μm width, 11~251 μm outer radius) are described. The circular ring lasers have been grown by metalorganic chemical vapor deposition, etched by SiCl₄ reactive ion etching, and planarized by polyimide. The dependences of laser threshold current density and peak emission wavelength (950~1015 nm) on outer radius are presented. The emission spectra show that the circular ring lasers lase mainly in high-order whispering gallery modes, with smaller outer radius ring lasers operating in low-order whispering gallery modes     

Modeling of short-pulse threshold voltage shifts due to DX centersin AlxGa1-xAs/GaAs and AlxGa1-xAs/InyGa1-yAs MODFET's

The DX-center-related short-pulse threshold voltage shifts (SPTVS) in Al_xGa_1-xAs-based MODFETs is modeled using CBAND, a simulator that solves Poisson equations self-consistently with Schrodinger equations and donor statistics. Using values given in the literature for the DX energy level in Al_xGa_1-xAs this technique gives good agreement between measured and simulated SPTVS for Al_0.3Ga_0.7As/GaAs and Al_0.3Ga_0.7As/In_0.2Ga_0.8As MODFETs. Both simulation and experiment show that the use of Al_0.2 Ga_0.8As in the donor layer reduces the SPTVS relative to the structures using Al_0.3Ga_0.7As. However, the measured shifts at this composition are considerably lower than the simulated values, indicating a DX energy level that may be higher than the value extrapolated from the literature, possibly due to the existence of multiple trap levels. Despite this discrepancy, these results support the use of strained-channel layers and lower Al_x Ga_1-xAs compositions in MODFETs for digital and other large-signal applications requiring good threshold stability     

Short pulse transfer characteristics of AlxGa1-xAs/GaAs andAlxGa1-xAs/InyGa1-yAsmodulation-doped heterojunction FET's

Short-pulse drain current versus gate voltage transfer characteristics measured for modulation-doped HFETs (MODFETs) with four donor-layer-channel-layer combinations-(1) Al_0.3Ga_0.7 As-GaAs, (2) Al_0.2Ga_0.8As-GaAs, (3) Al_0.3Ga_0.7As-In_0.2Ga_0.8As, and (4) Al_0.2Ga_0.8As-In_0.2 a_0.8 As-are compared with the DC transfer characteristics. The measurements are relevant to high-speed switching in HFET circuits. Significant shifts in threshold voltage are observed between the DC and short-pulse characteristics for the structures with n⁺-Al_0.3Ga_0.7As donor layers, while the corresponding shifts for structures with n⁺-Al_0.2Ga_0.8As donor layers are relatively small or virtually nonexistent     

微微秒Al_xGa_(1-x)As双异质结激光器

用宽度为300微微秒的电脉冲驱动质子轰击条形的Al_xGa_(1-x)As双异质结激光器,产生12微微秒光脉冲。并已经用来检测快速光电二极管的响应速率。     

InP-In1-xGaxAsyP1-yembedded mesa stripe lasers

A laser structure was fabricated using two-step liquid-phase epitaxy, employing the melt-back technique. The fabrication and properties of this structure are described in detail. Good linearity of the power output up to power levels of 20 mW was obtained. The threshold current density at 300 K is 9-12 kA/cm². This high value is mainly due to Zn-diffusion from the third to the buffer layer during the second growth step of the fabrication process. The external differential quantum efficiency is 30-35 percent under pulsed operation at 25°C. The pulsed threshold current has an exponential behavior with temperature whereT_{0} = 60degC. The far-field beam divergences in the directions parallel and perpendicular to the junction plane are12-15degand35-40deg, respectively. Transverse mode stabilization was improved with this laser structure.     

Fabrication of high-performance AlxGa1-xAs/InyGa1-yAs/GaAs resonant tunneling diodes using amicrowave-compatible technology

A microwave-compatible process for fabricating planar integrated resonant tunneling diodes (RTDs) is described. High-performance RTDs have been fabricated using Al_xGa_1-xAs/In_y Ga_1-yAs/GaAs strained layers. Peak-to-valley current ratios (PVRs) of 4.8:1 with simultaneous peak current densities of 4×10⁴ A/cm² have been achieved at room temperature for diodes of area 9 μm². Accurate measurements of reflection gain versus frequency between 1.5 and 26.5 GHz in the negative differential region indicate that the present technology is promising for millimeter-wave integrated circuits including self-oscillating mixers, frequency multipliers, and detectors     

Distributed Bragg-reflector Pb1-xSnxTe/PbSeyTe1-ydiode lasers

Distributed Bragg-reflector (DBR) diode lasers were designed and fabricated from lattice-matched Pb1-xSnxTe/PbSeyTe1-ysingle heterostructures grown by liquid-phase epitaxy. These DBR lasers operated in a single longitudinal mode within a limited range of heat-sink temperatures, 8.5-38 K, with a threshold current density of ∼3 kA/cm²at 20 K. Single longitudinal mode operation was maintained up to more than three times the threshold current. Continuous tuning of the laser output frequency over a range of ∼6 cm^-1, near 775 cm^-1(12.9 μm), was acheived by varying the heat-sink temperature. The average tuning rate was 0.21 cm^-1/K, and it was much smaller than the rate for corresponding Fabry-Perot lasers, which was 2.3 cm^-1/K. The measured effective mode index of the DBR lasers agrees well with the calculated one.     

GaAs-AlxGa1-xAs双异质结激光器的伏安特性

测量了77～300K 范围内 GaAs-AlxGa1-xAs DH 激光器的伏安特性。典型的正向特性曲线可用下式描写:I=I1+I2=Is1exp（AV）+Is1exp（q/nkT V）A 和 n 是只与温度有微弱关系的参数。     

In1-xGaxAsyP1-y/InP DH lasers fabricated on InP

In1-xGaxAsyP1-y/InP double heterostructure (DH) laser diodes with emission wavelengths of1.25-1.35mum at room temperature were fabricated on     

Properties of Mn-doped p-type InxGa1-xAsyP1-y grown by liquid-phase epitaxy

Epitaxial layers of p-type In_xGa_1-xAs_yP_1-y doped with Mn were grown by liquid-phase epitaxy on (111)-B oriented InP substrates at a growth temperature of 635°C. The doping characteristics and electrical and luminescent properties were studied and compared with those in Zn-doped epilayers. The distribution coefficient of Mn was about 0.1–0.3. The p-type epilayers with hole concentration of up to 3 × 10¹⁸ cm^?3 could be easily obtained by Mn doping. The activation energy of the Mn acceptor was about 40 meV. Mn doping yielded a broad photoluminescent emission spectrum which probably arises from d-shell interaction of the Mn as well as strong phonon coupling. From electron beam-induced current measurements in p-n heterojunctions utilizing Mn, a value of L_n = 2 μm was obtained for the minority carrier diffusion length of electrons in the p-type region.     

（AlxGa1—x）yIn1—yP Films an Its Optical Constants on the Surface

The optical parameters for three samples of intrinsic,doped Si and doped Mg（AlxGa1-x)yIn1-yP prepared by the MOCVD on GaAs substrate were measured by using ellipsometry and were calculated by the two-layer absorption film model.The results obtained were discussed.The grown rates and thickness of oxidic layer on the intrinsic（AlxGa1-x)yIn1-yP surface exposed in the atmosphere were studied.Alinear dependence of oxidic layer thickness on the time was obtained.     

GaxIn1-xAsyP1-y-InPtensile-strained quantum wells for 1.3-μm low-threshold lasers

Ga_xIn_1-xAs_yP_1-y-InP tensile-strained multiple quantum wells (MQWs) grown by low pressure metalorganic chemical vapor deposition (LP-MOCVD) are studied for the application to 1.3-μm lasers. High-resolution X-ray diffraction curves show good agreement with theoretical simulation. Clear energy separation of light hole and heavy hole bands is observed in the room temperature photoluminescence measurement. Threshold characteristics of -1.15% tensile-strained MQW lasers with graded index separate confinement heterostructure (GRINSCH) are investigated. The minimum threshold current density per well (J_th/N_w) for infinite cavity length obtained is 100 A/cm² for the device with a well number of 3. Tensile strain dependence of J_th/N _w for an infinite cavity is also clarified     

竖直液相外延炉生长Pb_(1-x)Sn_xTe/PbTe_(1-y)Se_y晶格匹配异质结激光器

本文根据Vagard定律,得到了Pb_(1-x)Sn_xTe/PbTe_(1-y)Se_y异质结晶格匹配条件,设计了生长参数,首次采用竖直液相外延炉生长了Pb_(1-x)Sn_xTe/PbTe_(1-y)Se_y品格匹配异质结,并制成了二极管激光器。     

Pb1-xSnxTe/PbTe1-ySeylattice-matched buried heterostructure lasers with CW Single mode output

The first successful realization of buried heterostructure diode lasers in the PbSnTe/PbTeSe system is reported. This has resulted in routine cw operation above 80 K with threshold currents as low as 60 mA in 5 µm wide stripe lasers. CW operation has been achieved to 120K. In addition, these lasers operate in the fundamental transverse mode up to as much as four times threshold.     

Influence of DX centers on the performance of unipolarsemiconductor lasers based on GaAs-AlxGa1-xAs

Optical and electrical characteristics of quantum cascade lasers, made in the GaAs-Al_xGa_1-xAs material system, show persistent changes at low temperatures, when devices are illuminated with an external white light. The magnitude of the effect is a function of the exposure time and finally saturates. The induced variation on the threshold current density of the lasers is more than 30%. This effect is related to the presence of deep donors (DX centers) in the high aluminum content AlGaAs cladding layers, which under illumination release electrons, thus increasing waveguide losses. By analyzing the light induced variations of the optical characteristics we were able to deduce the waveguide losses of our devices     

10 000-h continuous CW operation of In1-xGaxAsyP1-yInP DH lasers at room temperature

Life tests of In1-xGaxAsyP1-y/InP DH lasers fabricated from