A. Le Corre

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.

Electrical and optical properties of rare earth dopants (Yb, Er) in n-type III-V (InP) semiconductors

Rare earths (REs) diluted into MBE grown and synthesised n-type InP samples create an acceptor-like level (at 30 meV for Yb and 60 meV for Er) below the conduction band; the activation energies are deduced from temperature dependent Hall effect measurements. From EPR experiments where the authors observe resonance due to the Yb3+ ground state in n-type samples, they deduce that this acceptor-like level is not the Yb2+/Yb3+ acceptor level. They propose that the RE creates an attractive potential for electrons in III-V semiconductors. They discuss the consequences of this property for the luminescence excitation mechanism of the luminescence.

Pseudomorphic GaInP Schottky diode and high electron mobility transistor on InP

GaInP material has been used as a high‐gap semiconductor on InP to fabricate Schottky diodes. The experimental results show that the devices exhibit good electrical properties when the ternary strained layer is below the critical thickness. The best device is obtained with a gallium composition of 100% and a GaP thickness of 11 A, and exhibits a barrier height of 0.8 eV, an ideality factor of 1.1, and a reverse current of 0.1 nA at −1 V. A high electron mobility transistor has been fabricated on an InP substrate by molecular beam epitaxy using a high‐gap GaInP material, and a transconductance of 300 mS/mm has been measured on a device of 1.3 μm gate length.

Growth of matched metallic ErP0.6As0.4 layers on GaAs in a molecular beam epitaxy system

Metallic layers of ErP0.6As0.4 have been grown by molecular beam epitaxy on GaAs at 500 °C. The growth has been achieved by adjusting the PH3 and AsH3 flows to obtain a good lattice match to the substrate, the erbium flux remaining below the flux of the V elements. The 10–100 nm thick epitaxial layers reproducibly showed lattice mismatch below 5×10−4 and unlike the ErAs layers, they do not degrade in the atmosphere. Due to its low resistivity (ρ=80 μΩ cm), this compound is an ideal candidate for the realization of epitaxial III‐V semiconductor/metal/III‐V semiconductor heterostructures.

Direct correlation of structural and optical properties of InAs self-assembled dots deposited on InP(100)

The optical properties of self-assembled InAs dots on InP have been measured by photoluminescence, and using a selective chemical etching of the InP cap layer, the geometrical properties of the same dots have been determined by atomic force microscopy. From the dot dimensions, the calculated (n=1) electron to heavy hole transition energies with a simple model are strongly correlated to the measured photoluminescence spectra. This technique allows a better understanding of the correlation between structural and optical properties of self-assembled dots.

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.

Formation of low-index facets in Ga0.2In0.8As and InAs islands on a InP(113)B substrate

Strained Ga0.2In0.8As and InAs islands were grown on a InP(113)B substrate by gas source molecular beam epitaxy and examined by transmission electron microscopy and atomic force microscopy. The islands are mainly bounded by the low-index facets {001}, {111}B, and {110} [inclination with respect to the (113)B surface of 25°, 29°, and 31°, respectively]. Some of the consequences of the substrate orientation on the island shape and formation are discussed.

Excitation mechanisms of rare earth (Yb) luminescence in III-V semiconductors (InP)

Thermal dependent Hall effect and time-resolved band edge photoluminescence on rare earth (Yb) doped indium phosphide are reported. The presence of two different traps related to the rare earth clearly demonstrated A very efficient trapping is observed in time resolved photoluminescence. The variations of the band edge luminescence decay time with temperature and excitation density lead the authors to consider the trapping of both electrons and holes on the rare earth site. They propose a model based on the creation of bound exciton trapped on the rare earth site which allows them to account for both the electrical and optical properties of rare earth in III-V compounds. The reasonable quantitative agreement between this model, time-resolved and cw photoluminescence data is shown and discussed.

Fe-doped InGaAs/InGaAsP photorefractive multiple quantum well devices operating at 1.55 μm

Results on semi-insulating photorefractive multiple quantum well (MQW) devices operating without trapping layers are reported. The device structure consists of a MQW doped with Fe (1017 cm−3) isolated from the doped contact by intrinsic standoff layers. The photocarriers generated by the pump pulse are trapped in the MQW and screen the applied electric field in the MQW. Output diffraction efficiency of 0.2% is measured in a nondegenerate four-wave-mixing configuration and the rise time of the diffraction signal reaches 200 ns.