A low-threshold polarization-controlled vertical-cavitysurface-emitting laser grown on GaAs (311)B substrate

We have demonstrated a GaAs (311)B vertical-cavity surface-emitting laser (VCSEL) with a threshold current as low as 250 μA, which is the lowest value ever reported for that on non-(100) oriented substrates. Also, the fabricated VCSEL shows a stable polarization state for wide during current ranges and a large polarization-mode suppression ratio over 30 dB between the [2¯33] and [011¯] axis modes at 5 mA. The electrical specific resistance of 1.2×10^-4 Ω·cm^-2 at the threshold was reasonably low due to carbon autodoping to AlAs in a p-type distributed Bragg reflector (DBR)     

High-power 980-nm AlGaAs/InGaAs strained quantum-well laser grown by OMVPE

High-power lattice-strained AlGaAs/InGaAs graded index separate-confinement heterostructure (GRINSCH) quantum-well lasers emitting at a 980-nm wavelength have been grown by organometallic vapor phase epitaxy (OMVPE) and fabricated with a self-aligned ridge-waveguide structure. Using a 3- mu m-wide and 750- mu m-long AR-HR coated laser, 30 mV of optical power was coupled into optical fibers with 28.6% efficiency. A dominating single-lobe far-field radiation pattern was obtained from a wedge-shaped ridge-waveguide laser for output power as high as 240 mW with a maximum output power of 310 mW.<>     

An InGaAs-GaAs vertical-cavity surface-emitting laser grown on GaAs(311)A substrate having low threshold and stable polarization

We have fabricated an InGaAs-GaAs vertical-cavity surface-emitting laser (VCSEL) grown on a GaAs(311)A substrate by molecular beam epitaxy (MBE) and demonstrated continuous wave operation at room temperature. A threshold current density of 80 A/cm/sup 2//well and very stable polarization characteristics up to 2.7 times the threshold were achieved. The polarization state with the highest optical intensity was oriented along the [2~33] direction, which is the crystallographic axis exhibiting the maximum gain. An extinction ratio of more than 12.7 dB was obtained between two orthogonal polarization states. The high and anisotropic gain of a (311)A-oriented VCSEL will drastically improve the device performance by optimization and process engineering.     

Investigation of dynamic polarization stability of 850-nmGaAs-based vertical-cavity surface-emitting lasers grown on (311)B and(100) substrates

The polarization stability of 850-nm GaAs-based vertical-cavity surface-emitting lasers (VCSELs) under dynamic operation was investigated by comparing the characteristics of VCSELs grown on (311)B and (100) GaAs substrates. Significantly larger suppression ratios of the two orthogonal polarization modes was obtained for VCSELs on (311)B substrates than those on (100) substrates under zero-bias modulation. Time-dependent orthogonal polarization suppression ratio measurements also showed that the polarization direction was more stable in the VCSEL on (311)B substrates than that on (100) substrates. Error-free transmission was realized from VCSELs on (311)B substrates with and without a polarizer in both back-to-back and 100-m multimode fiber transmission     

Single-transverse mode and stable-polarization operation underhigh-speed modulation of InGaAs-GaAs vertical-cavity surface-emittinglaser grown on GaAs (311) B substrate

We have demonstrated an oxide confinement vertical-cavity surface-emitting laser grown on a GaAs (311)B substrate, and achieved single-transverse mode and single-polarization operation in the entire tested current range. The threshold was 0.6 mA for a 2.7 μm×2.9 μm oxide aperture. Even under high-speed modulation up to 5 GHz, the device showed stable single-transverse mode and polarization. Sidemode suppression ratio and orthogonal polarization suppression ratio were over 30 and 10 dB, respectively     

Room-temperature pulsed operation of AlGaAs/GaAs vertical-cavitysurface-emitting laser diode on Si substrate

Room-temperature pulsed AlGaAs/GaAs vertical-cavity surface-emitting laser diode (VCSELD) has been grown on Si substrate using metalorganic chemical vapor deposition. The VCSELD structure grown on Si substrate consists of a single quantum well active layer and a 20-pair of AlAs/GaAs distributed Bragg reflector (DBR). The measured reflectivity of the 20-pair of AlAs/GaAs DBR was 93% at the wavelength of 860 nm. The VCSELD on Si substrate exhibited a threshold current of 79 mA and a threshold current density of 4.9 kA/cm² under pulsed condition at room temperature     

Optical properties of GaAs/AlAs superlattices grown on (311)A GaAs surfaces

We present a temperature-dependence photoluminescence of (GaAs)₅/(AlAs)₅ superlattice grown on (311)A-oriented semi-insulating substrate by molecular beam epitaxy. The temperature dependence reveals an anomalous decrease of the PL width, which is explained in terms of phonon-assisted thermal activation of localized excitons.     

Influence of substrate misorientation on the optical and structural properties of InGaAs/GaAs single strained quantum wells grown on (111)B GaAs by molecular beam epitaxy

A series of InGaAs/GaAs Single Strained Quantum Wells (SSQWs) with indium content ranging from 25% to 35% and 100 Å well thickness were grown on two different (111)B GaAs off-axis substrates under optimized growth conditions for simultaneous growth. Optoelectronic properties were studied in terms of low temperature photoluminescence (PL). Results indicate a PL emission dependence with the substrate used, this dependence being stronger for highly strained systems. In order to determine the source of this dependence, samples were studied by Planar View Transmission Electron Microscopy (PVTEM). Relaxation mechanisms seem to act in a different way regarding the misoriented substrate used. Although previous theoretical results have already reported this dependence, this is the first direct evidence of this phenomenon for SSQWs. The results of these two different techniques will be compared and discussed.     

Structure of heterointerfaces and photoluminescence properties of GaAs/AlAs superlattices grown on (311)A and (311)B surfaces: Comparative analysis

The photoluminescence properties of type II GaAs/AlAs superlattices grown on the (311) surface are determined by their polarity. Previous HRTEM investigations demonstrated a corrugation (with height of 1 nm and period of 3.2 nm) of both GaAs/AlAs and AlAs/GaAs interfaces in samples grown on the (311)A surface. In the present study, a lateral periodicity of 3.2 nm is also revealed in HRTEM images of a superlattice grown on the (311)B surface and in their Fourier transforms. However, this periodicity is poorly pronounced, which is due to fuzzy corrugation and the presence of a long-wavelength (>10 nm) disorder. Photoluminescence spectra of the GaAs/AlAs superlattice on the (311)A surface are strongly polarized relative to the direction of interface corrugation, in contrast to the (311)B superlattice, in which the corrugation is weakly pronounced. It was found that the strong mixing between the Θ and X minima of the conduction band, occurring only in sublattices with strongly corrugated interfaces, allows generation of bright red luminescence at 650 nm up to room temperature. The distinctions revealed between the superlattices grown on the (311)A and (311)B surfaces confirm that it is precisely the interface corrugation, and not crystallographic orientation, that governs the optical properties of (311) superlattices.     

Room-temperature laser emission of GaInNAs-GaAs quantum wells grown on GaAs (111)B

In this work, we present room-temperature laser emission at 1.206 /spl mu/m from GaInNAs-GaAs quantum-well (QW) laser diodes (LDs) grown on misoriented GaAs (111)B substrates for the first time. Details of the structure and the molecular beam epitaxial growth of the lasers are discussed. We found that the postgrowth rapid thermal annealing increased the optimum emission, while the in situ self annealing effect in these QWs is almost negligible. The optimum annealing cycle (30 s at 850/spl deg/C) is comparable to that found for the cladding-free GaInNAs single QW samples grown on GaAs (111)B. Finally, the optical and electrical characterization of these LD devices is presented. The LDs show a room-temperature threshold current density of 2.15 kA/cm/sup 2/, with a differential quantum efficiency of 37%, under pulsed conditions.     

The growth of high mobility heterostructures on (311)B GaAs

We demonstrate that the (311)B surface of GaAs can be used for the fabrication of high mobility (μ 2.4 × 10⁶ cm² V⁻¹ s⁻¹) two-dimensional electron gases, in which the mobility is found to be anisotropic with μ_{[ 33]} > μ_{[01 ]}. This paper reviews the magneto-transport properties of the (311)B system and sheds light on the nature of the scattering mechanisms determining the electron mobility. These results are of particular relevance to the current discussion of the nature of the {311} surface.

It is well known that a similar mobility anisotropy exists in hole gases grown on the (311)A surface, although attempts to interpret such results are complicated by the anisotropic and non-parabolic nature of the valence band structure. For electron gases grown on the (311)B surface we demonstrate experimentally (with ballistic focusing) that the Fermi surface is isotropic, leading to the conclusion that the most likely cause of the mobility anisotropy is anisotropic interface roughness scattering. This is also confirmed by measurements of mobility as a function of carrier density, which can be fitted by a simple interface roughness scattering theory.

Further experiments have demonstrated that ballistic quantization can be observed in both [ 33] and [01 ] directions, despite the large differences in anisotropic mobility.     

InGaAs/GaAs vertical-cavity surface-emitting lasers on (311)B GaAssubstrate

InGaAs/GaAs vertical cavity top-emitting dielectric-mirror surface-emitting lasers have been fabricated on a (311)B GaAs substrate. The threshold current was 25 mA at a lasing wavelength of 0.97 μm under pulsed operation at room temperature. The output was linearly polarised in the [2¯33] direction     

Optical investigation of the relaxation process in InGaAs/GaAs single strained quantum wells grown on (001) and (111)B GaAs substrates

Molecular Beam Epitaxy (MBE) growth of a series of Single Strained Quantum Wells (SSQWs) of InGaAs/GaAs with indium content ranging from 10% to 35% and 100 Å well thickness was performed on (001) and (111)B GaAs substrates under optimized growth conditions for simultaneous growth. The Critical Layer Thickness (CLT) of the heterostructures grown on both substrates was comparatively studied by low temperature Photoluminescence (PL). Relaxation is readily observed in the structures grown on (001) GaAs for 24% In-content. This value is in close agreement with both a calculation of the excess strain associated with the two Matthews and Blakeslee strain relieving dislocation mechanisms and the onset of three-dimensional growth. By contrast, heterostructures grown on (111)B GaAs remain pseudomorphic for In-contents above 25%. A maximum PL peak wavelength of 1.1 microns at room temperature has been reached under the growth conditions used. This would correspond to an In-content around 31%. The study shows that (111)B is a preferable choice of substrate orientation for the growth of InGaAs/GaAs heterostructures for optoelectronic applications at wavelengths beyond 1 μm.     

Self-organization phenomenon of strained InGaAs on InP (311) substrates grown by metalorganic vapor phase epitaxy

We have demonstrated that a self-organization phenomenon occurs in strained InGaAs system on InP (311) substrates grown by metalorganic vapor phase epitaxy. This suggests that a similar formation process of nanocrystals exists not only on the GaAs (311)B substrate but also on the InP (311)B substrate. However, the ordering and the size homogeneity of the self-organized nanocrystals are slightly worse than those of the InGaAs/AlGaAs system on the GaAs (311)B substrate. The tensilely strained condition of a InGaAs/InP system with growth interruption in a PH₃ atmosphere reveals a surface morphology with nanocrystals even on the InP (100) substrate. It was found that strain energy and high growth temperature are important factors for self-organization on III-V compound semiconductors. Preliminary results indicate that the self-organized nanostructures in strained InGaAs/InP systems on InP substrates exhibit room temperature photoluminescent emissions at a wavelength of around 1.3 p.m.     

Formation of a step-free InAs quantum well selectively grown on a GaAs (111)B substrate

We investigated the possibility of forming a step-free quantum well structure. A step-free InAs monolayer was grown on a selectively grown mesa by controlling surface phases with in-situ monitoring of surface photo-absorption. We selectively grew a GaAs buffer at 800°C and cooled the sample keeping the (2×2)-like As stabilized surface. Atomic force microscopy (AFM) observation demonstrated that fully step-free surfaces were formed on the 8 μm wide mesa. Then, a monolayer-thick InAs was formed on this step-free surface and this InAs layer was capped by GaAs under the (2×2)-like condition. The quantum level of the step-free InAs layer was evaluated by spatially resolved photoluminescence (μPL) measurement. Uniform PL intensity and the lack of a double layer peak indicated the formation of a step-free InAs quantum well, which was in good agreement with AFM observation.     

GaInP/AlGaInP double-heterostructure laser grown on a(111)B-oriented GaAs substrate by metalorganic chemical vapourdeposition

Room temperature continuous-wave operation of a Ga_0.5In _0.5P/(Al_0.5Ga_0.5)_0.5In _0.5P double-heterostructure laser grown on a (111)B-oriented GaAs substrate by metalorganic chemical vapour deposition was obtained for the first time. The threshold current was 99 mA. The emission wavelength was around 650 nm, which was about 30 nm shorter than that of a similar laser grown on a (100)-oriented GaAs substrate     

Comparison of steady-state and transient characteristics oflattice-matched and strained InGaAs-AlGaAs (on GaAs) and InGaAs-AlInAs(on InP) quantum-well lasers

Numerical techniques are developed to study the output spectra and to solve the multimode coupled rate equations including transverse electric (TE) and transverse magnetic (TM) propagations for In_x Ga_1-xAs-Al_0.3Ga_0.7As and In_0.53+xGa_0.47-xAs-Al_0.48In_0.52 quantum-well lasers. Optical properties are calculated from a 4×4 k×p band structure, and strain effects are included with the deformation potential theory. It is found that an introduction of 1.4% compressive strain to the quantum well results in roughly 3-4 times improvement in the intrinsic static characteristics in terms of lower threshold current, greater mode suppression and lower nonlasing photon population in the laser cavity. The authors identify the effect of strain on the large signal temporal response. They also include calculated CHSH Auger rates in their model     

Observation of the pyroelectric effect in strained piezoelectric InGaAs/GaAs quantum-wells grown on (111) GaAs substrates

We investigated the temperature dependence of the piezoelectric constant e₁₄, i.e. the pyroelectric effect, of various strained InGaAs/GaAs single- and multi-quantum wells embedded in p-i-n structures grown on (111)B GaAs substrates and diodes made from these structures. Both photoreflectance spectroscopy and differential photocurrent spectroscopy were applied to obtain e₁₄ over the temperature range 11-300 K. The values of e₁₄ for In_xGa_1−xAs quantum well layers with x=0.12-0.21 were observed to increase with temperature, which is contrary to the expected dependence, and the strain-induced components of the pyroelectric coefficients were quantitatively determined. The dependence of the pyroelectric coefficient on In fraction is discussed.     

Design analysis of 1550-nm GaAsSb-(In)GaAsN type-II quantum-well laser active regions

A novel active region design is proposed to achieve long-wavelength (/spl lambda/ = 1550-nm) diode lasers based on a type-II quantum-well (QW) design of (In)GaAsN-GaAsSb grown on a GaAs substrate. The strain-compensated structures hold potential as an ideal active region for 1500-nm GaAs-based vertical cavity surface emitting lasers. A design analysis and optimization of 1550-nm emitting structures is presented. An optimal type-II multiple-QW design allows for electron-hole wavefunction overlaps of greater than 50%.     

Study of metamorphic InGaAs/GaAs quantum well laser materials grown on GaAs substrate by molecular beam epitaxy

The GaAs based InGaAs metamorphic structures and their growth by molecular beam epitaxy (MBE) are investigated. The controlling of the source temperature is improved to realize the linearly graded InGaAs metamorphic structure precisely. The threading dislocations are reduced. We also optimize the growth and annealing parameters of the InGaAs quantum well (QW). The 1.3-μm GaAs based metamorphic InGaAs QW is completed. A 1.3-μm GaAs based metamorphic laser is reported.