S. Salaun

Relationship between self‐organization and size of InAs islands on InP(001) grown by gas‐source molecular beam epitaxy

Using the strained‐induced 2D–3D transition, InAs dots have been grown on InP(001) and examined by transmission electron microscopy. Two different modes of island size and spatial distribution have been identified. For deposit of 1.5 and 1.8 monolayers, the islands are about 7 nm high and randomly distributed. Above 2 monolayers, they are about five times smaller in volume and locally self‐organized, with a typical distance of 40 nm independent of the island density. It is suggested that the strong dependence of the island size on the total amount of deposited InAs is mainly due to long range interactions through the substrate.

Strain in InAs islands grown on InP(001) analyzed by Raman spectroscopy

Raman scattering has been used to investigate strained InAs islands grown on InP(001), in correlation with transmission electron microscopy. Symmetry arguments, selective resonance at the InAs E1‐like transition and comparison with a single‐quantum‐well structure allowed to distinguish between the islands and remaining wetting layer signals. Whereas the vibrational modes of the 2D thin layers are greatly affected by interface roughness and confinement, strain effects mainly account for the phonon frequency shifts in the islands.

GaPSb: A new ternary material for Schottky diode fabrication on InP

Despite its excellent transport properties, the low value of the Schottky barrier height on n‐ type InP (0.43 eV) prevents its use in electronic applications. A new InP lattice‐ matched material (GaPSb with 65% Sb) has been grown for the first time by gas source molecular beam epitaxy and studied. The material gap is 0.9 eV and the gold Schottky diode reaches 0.6 eV on this compound. This is the highest barrier ever reported on InP lattice‐matched materials which do not contain aluminum. Continuous and picosecond luminescence results show that the GaPSb/InP is a type II heterostructure with ΔEc=50 meV at 4 K.

Tunable narrowband optical filter in photorefractive InGaAsP:Fe/InP:Fe singlemode waveguide

Recently a new compact WDM spectrum analyser without moving parts was demonstrated using a bulk photorefractive InP:Fe crystal. With the aim of reducing the sweeping time by confining optical energy, a first optically tunable filter on a photorefractive singlemode waveguide was realized on an InP:Fe substrate. The device operates at the 1.55 /spl mu/m wavelength and the tuning range is given by the tunable laser diode used for the control of the Bragg grating period. The bandwidth is 0.02 nm (2.5 GHz) and the intrinsic reflectivity is 2%.

Critical layer thickness of In0.82Ga0.18As/InP quantum wells

Abstract We present results on a study of strained In 0.82 Ga 0.18 As/InP quantum wells (QWs) grown by gas source MBE. From transmission electron microscopy, we find that the onset of dislocation creation occurs for thickness around 60 A. Strain release is found to induce a dramatic effect on the carrier lifetime as shown by time-resolved photoluminescence technique: lifetimes values of 2 ns are measured on QWs with thickness of 18 and 40 A, but drop to 60 ps on a 64 A thick QW.

Photorefractive semiconductor single-mode waveguides grown by gas-source molecular-beam epitaxy.

Two semiconductor single-mode waveguides have been fabricated to study the photorefractive effect in epilayers grown on an InP:Fe substrate. The first experimental results obtained in these structures are reported. At 1.55-microm wavelength, a 0.53-cm(-1) gain is observed in contradirectional two-wave mixing and a 4-cm(-1) gain is measured in codirectional two-wave mixing with a 5.7-kV/cm applied field. The gain dependence versus the light intensity and the applied field is also discussed.

Photorefractive singlemode waveguide on InP:Fe substrate

A singlemode optical waveguide presenting photorefractive behavior has been developed on a InP:Fe substrate. The slab waveguide is characterized by two-wave mixing. The coupling gain reaches 2.2 cm/sup -1/ (9.5 dB/cm) under a 5 kV/cm electric field when operating at 1.55 /spl mu/m wavelength.<<ETX>>

Scanning photoluminescence characterization of iron-doped gas source molecular beam epitaxy indium phosphide layers

Abstract Iron-doped indium phosphide layers were grown by gas source molecular beam epitaxy with a high purity solid iron source. The iron concentration varied from some 10 16 cm −3 to a few 10 19 cm −3 . N-i-n or n + -i-n + layer structures were realized on two types of substrate: semi-insulating or n + . Some iron-doped layers were also produced directly on a semi-insulating substrate. Resistivity values of 10 3 Ω cm to 10 8 Ω cm were obtained, depending on the iron concentration. The iron incorporation was found to be related to the growth conditions, especially the iron cell temperature and the growth substrate temperature. The layers were characterized by secondary ion mass spectrometry and scanning photoluminescence measurements at room temperature. The latter technique used either photoluminescence integrated signal measurements or recorded InP spectra. The photoluminescence intensity was found to be a valuable parameter for evaluating the iron incorporation. For layers having the highest resistivities, obtained at iron concentrations of a few 10 17 cm −3 , the photoluminescence intensity was comparable with that obtained for bulk semi-insulating substrates, and the density of defects was found to be (2–5) × 10 4 cm −2 .

Lateral diffusion of carriers and screening measurements in GaInAsP/GaInAs MQW photorefractive devices at 1.55 /spl mu/m

We demonstrate the performance of a semiconductor photorefractive p-i-n diode operating at 1.55 /spl mu/m in the longitudinal quantum-confined Stark geometry. The device structure consists of a semi-insulating GaInAsP/GaInAs multiple quantum well, sandwiched between two trapping regions, and embedded in a p-n junction. On this structure, we investigated the carrier lateral diffusion, the applied electric field screening and the diffraction efficiency.

In/sub 1-x/Ga/sub x/As/In/sub .53/Ga/sub .47/As strained superlattices grown by gas source molecular beam epitaxy

Strained epitaxial heterostructures yield attractive optoelectronic properties for laser diodes and optical amplifiers. Using various characterization techniques consisting of continuous and time resolved photoluminescence, X-ray diffraction, and transmission electron microscopy, the authors demonstrate the importance of the growth temperature on the relaxation of strained superlattices (SL). By lowering the growth temperature, high quality highly strained SL layers could be obtained.<<ETX>>