Structural and optical properties of InAs/In0.52Al0.48As self-assembled quantum wires on InP(001)

Six-stacked InAs/In0.52Al0.48As self-assembled quantum wires (QWRs) on InP(001) by molecular-beam epitaxy (MBE) have been studied by high-resolution transmission electron microscopy (HRTEM) and polarized PL measurements. We obtained the chemical lattice fringe (CLF) image of InAs self-assembled QWRs embedded in the In0.52Al0.48As matrix by the interference between the (002)-diffracted beam and the transmitted beam in the image plane of the objective lens. The results show that the InAs QWRs were bounded by (113), (001) and (114) facets. Both the size and strain distribution in QWRs were determined. It was found that with the growth of successive periods, the height and height fluctuation of InAs QWRs decreased from the bottom period to the upper one. Some suggestions are put forward for further improving the uniformity of the stacked InAs QWRs. (c) 2005 Elsevier B.V. All rights reserved.

Influence of rapid thermal annealing on InAs/InAlAs/InP quantum wires with different InAs deposited thickness

We have studied the effect of the post-growth rapid thermal annealing on optical and electrical properties of InAs/InAlAs/InP quantum wires with various InAs deposited thickness. Quite different annealing behaviors in photoluminescence and dark resistance are observed, which can be attributed to dislocations in samples. After annealing at 800 degrees C, quantum wires still exist in the sample with two monolayer InAs deposited thickness, but the temperature-dependent PL properties are changed greatly due to the intermixing of In/Al atoms. (c) 2005 Elsevier B.V. All rights reserved.

Raman study on self-assembled InAs/InAlAs/InP(001) quantum wires

The phonons of self-assembled InAs/InAlAs/InP quantum wires (QWRs) have been studied by Raman scattering. The QWR LO phonons show an unusual frequency shift with the increase of the InAs deposited thickness due to dislocations. The QWR LO phonons are found to follow the selection rule of the LO phonons in bulk zinc-blende semiconductors. Because of the intermixing of In/Al atoms and the multiplication of dislocations, the post-growth thermal annealing treatment leads to a shift of the QWR LO phonons to lower frequency.

Self-organized superlattices along the [001] growth direction in In0.52Al0.48As layers grown on nominally (001) InP substrates by molecular beam epitaxy

Horizontal self-organized superlattice structures consisting of alternating In-rich and Al-rich layers formed naturally during solid-source molecular beam epitaxy (MBE) growth of In0.52Al0.48As on exactly (001) InP substrates, with In and At fluxes unchanged. The growth temperatures were changed from 490 to 510 degrees C, the most commonly used growth temperature for In0.52Al0.48As alloy. No self-organized superlattices (SLs) were observed at the growth temperature 490 degrees C, and self-organized SLs were observed in InAlAs layers at growth temperatures ranging from 498 to 510 degrees C. The results show that the period of the SLs is very highly regular, with the value of similar to 6 nm, and the composition of In or Al varies approximately sinusoidally along the [001] growth direction. The theoretical simulation results confirm that the In composition modulation amplitude is less than 0.02 relative the In composition of the In0.52Al0.48As lattice matched with the InP substrate. The influence of InAs self-organized quantum wires on the spontaneously formed InxAl1-xAs/InyAl1-yAs SLs was also studied and the formation of self-organized InxAl1-xAs/InyAl1-yAs SLs was attributed to the strain-mediated surface segregation process during MBE growth of In0.52Al0.48As alloy. (C) 2005 Published by Elsevier Ltd.

Growth of a periodic InP-based heteroepitaxial structure for a quantum cascade laser

The route to grow InP-based heteroepitaxial structure for quantum cascade laser by molecular beam epitaxy is reported. Optimized growth conditions including substrate temperature, V/III ratio, growth rates, doping levels and interface control are summarized. Double crystal Xray diffraction and cross-sectional transmission electron microscopy disclose that our grown InP-based heteroepitaxial structure for quantum cascade laser has excellent periodicity and sharp interfaces. (C) 2005 Elsevier B.V. All rights reserved.

Monolithic integration of an InGaAsP-InP strained DFB laser and an electroabsorption modulator by ultra-low-pressure selective-area-growth MOCVD

The design and basic characteristics of a strained InGaAsP-InP multiple-quantum-well (MQW) DFB laser monolithically integrated with an electroabsorption modulator (EAM) by ultra-low-pressure (22 mbar) selective-area-growth (SAG) MOCVD are presented. A fundamental study of the controllability and the applicability of band-gap energy by using the SAG, method is performed. A large band-gap photoluminescence wavelength shift of 88 mn. was obtained with a small mask width variation (0-30 mu m). The technique is then applied to fabricate a high performance strained MQW EAM integrated with a DFB laser. The threshold current of 26 mA at CW operation of the device with DFB laser length of 300 mu m and EAM length of 150 mu m has been realized at a modulator bias of 0 V. The devices also exhibit 15 dB on/off ratio at an applied bias voltage of 5 V.

Photoluminescence characteristics of InP annealed in phosphorus and iron phosphide ambiences

Photo luminescence (PL) spectroscopy has been used to study InP annealed in phosphorus and iron phosphide ambiences. Noticeable PL emissions related with thermally induced defects have been detected in undoped InP annealed in iron phosphide ambience. Origins of the PL emissions have been discussed. (c) 2004 Elsevier Ltd. All rights reserved.

Fabrication of arrayed waveguide grating based on SOI material

An arrayed waveguide grating based on SOI material was fabricated by inductive coupled plasma (ICP) etching technology. The central wavelength of the device was designed at 1.5509 mu m and the channel spacing was 200 GHz. Comparing with the values of the design, the differences of the central wavelength and the channel spacing in the test were 0.28 nm and 0.02 nm, respectively. The adjacent channel crosstalk was about 10 dB, and the uniformity of the five channels' insertion loss was only 0.7 dB. The results show that the device can be used as a demultiplexer.

Effect of layer thickness of immiscible alloy In0.52Al0.48As on the morphology of InAs nanostructure grown on In0.52Al0.48As/InP(001)

Thickness effect of immiscible alloy InAlAs as matrix layer on the morphology of InAs nanostructure grown on InAlAs/InP (0 0 1) by solid-source molecular-beam epitaxy has been studied. Experiments demonstrate that InAs nanostructure grown on thin InAlAs matrix layer forms randomly distributed quantum dot, whereas, grown on thick InAlAs matrix layer forms one-dimension ordered mixture of quantum wire and quantum dot. This drastic modification in the nanostructure morphology is attributed to the generation of composition modulation in the immiscible InAlAs alloy with the increase of the layer thickness. (C) 2004 Elsevier B.V. All rights reserved.

Photonic crystal vertical-cavity surface-emitting laser based on GaAs material

A photonic crystal vertical-cavity-surface-emitting laser ( PC-VCSEL) with a wavelength of about 850 nm was realized. The direct-current electrically-driven PC-VCSELs with a minimum threshold current of 2 mA and a maximum threshold current of 13.5 mA were obtained. We fabricated a series of PC-VCSEL chips whose lattice constants are in the range from 0.5 to 3 mu m with different filling factors, and found that the laser characterization depends on the lattice constant, the filling factor, the size of cavity, etc.

Room-temperature continuous-wave electrically injected InP-GaInAsP equilateral-triangle-resonator lasers

Equilateral-triangle-resonator (ETR) microlasers with an output waveguide connected to one of the vertices of the ETR are suitable to be a light source for photonic integrated circuits. InP-GaInAsP ETR lasers with side length from 10 to 30 pm and the output-waveguide width of 1 or 2 pm are fabricated using standard photolithography and inductively coupled-plasma etching techniques. Continuous-wave electrically injected 1520-nm ETR laser with 20-mu m sides is realized with the maximum output power 0.17 and 0.067 mW and the threshold current 34 and 43 mA at 290 K and 295 K, respectively.

Effect of substrate misorientation on the InAs/InAlAs/InP nanostructure morphology and lateral composition modulation in the InAlAs matrix

The authors report the self-organized growth of InAs/InAlAs quantum wires on nominal (001) InP substrate and (001) InP substrates misoriented by 2 degrees, 4 degrees, and 8 degrees towards both [-110] and [110]. The influence of substrate misorientation on the structural and optical properties of these InAs/InAlAs quantum wires is studied by transmission electron microscopy and photoluminescence measurements. Compared with that grown on nominal (001) InP substrate, the density of InAs/InAlAs quantum wires grown on misoriented InP(001) substrates is enhanced. A strong lateral composition modulation effect take place in the InAlAs buffer layers grown on misoriented InP substrates with large off-cut angles (4 degrees and 8 degrees), which induces a nucleation template for the first-period InAs quantum wires and greatly improve the size distribution of InAs quantum wires. InAs/InAlAs quantum wires grown on InP (001) substrate 8 degrees off cut towards [-110] show the best size homogeneity and photoluminescence intensity. (c) 2007 American Institute of Physics.

Generation and suppression of deep level defects in InP

Deep level defects in as-grown and annealed n-type and semi-insulating InP have been studied. After annealing in phosphorus ambient, a large quantity of deep level defects were generated in both n-type and semi-insulating InP materials. In contrast, few deep level defects exist in InP after annealing in iron phosphide ambient. The generation of deep level defects has direct relation with in-diffusion of iron and phosphorus in the annealing process. The in-diffused phosphorus and iron atoms occupy indium sites in the lattice, resulting in the formation of P anti-site defects and iron deep acceptors, respectively. T e results indicate that iron atoms fully occupy indium sites and suppress the formation of indium vacancy and P anti-site, etc., whereas indium vacancies and P anti-site defects. are formed after annealing in phosphor-us ambient. The nature of the deep level defects in InP has been studied based on the results.

Inductively coupled plasma etching of two-dimensional InP/InGaAsP-based photonic crystal

Inductively coupled plasma (ICP) etching of InP in Cl-2/BCl3 gas mixtures is studied in order to achieve low-damage and high-anisotropy etching of two-dimensional InP/InGaAsP photonic crystal. The etching mechanisms are discussed and the effect of plasma heating on wafer during etching is analyzed. It is shown that the balance between the undercut originating from plasma heating and the redeposition of sputtering on the side-wall is crucial for highly anisotropic etching, and the balance point moves toward lower bias when the ICP power is increased. High aspect-ratio etching at the DC bias of 203 V is obtained. Eventually, photonic crystal structure with nearly 90 degrees side-wall is achieved at low DC bias after optimization of the gas mixture.

Influence of deep level defects on electrical compensation in semi-insulating InP materials

In this paper, we analyze and compare electrical compensation and deep level defects in semi-insulating ( SI) materials prepared by Fe-doping and high temperature annealing of undoped InP. Influence of deep level defects in the SI-InP materials on the electrical compensation has been studied thermally stimulated current spectroscopy (TSC). Electrical property of the Fe-doped SI-InP is deteriorated due to involvement of a high concentration of deep level defects in the compensation. In contrast, the concentration of deep defects is very low in high temperature annealed undoped SI-InP in which Fe acceptors formed by diffusion act as the only compensation centre to pin the Fermi level, resulting in excellent electrical performance. A more comprehensive electrical compensation model of SI-InP has been given based on the research results.