B. Sermage

Comparison of Auger recombination in GaInAs-AlInAs multiple quantum well structure and in bulk GaInAs

Carrier lifetime has been measured in GaInAs-AlInAs multiple quantum well structures and in thick GaInAs samples for local carrier densities between 2 \times 10^{17} and 5 \times 10^{19} cm-3. Carrier lifetime and Auger recombination are found to be very close (±20 percent) in the two structures. The Auger limited T 0 values calculated for DH and MQW lasers are found to be, respectively, 93 and 170 K. Optimization of the quantum well laser as a function of the number of wells in the active region is discussed.

High-Quality InGaAsN Growth by Metalorganic Vapor-Phase Epitaxy Using Nitrogen Carrier Gas and Dimethylhydrazine, Tertiarybutylarsine as Group V Precursors

We have successfully grown GaAsN and InGaAsN layers on GaAs substrate using atmospheric-pressure metalorganic vapor-phase epitaxy (MOVPE). Dimethylhydrazine and tertiarybutylarsine have been employed as sources of nitrogen and arsenic, respectively. To investigate the incorporation behavior of nitrogen [N] in GaAsN and InGaAsN layers as a function of ambient gas in the reactor, growth was performed in the presence of hydrogen H2 and nitrogen N2 gases. Good structural quality and surface morphology have been obtained with both gases. Furthermore, with N2 ambient gas, an enhancement of nitrogen incorporation has been observed. The nonradiative carrier lifetime is about 25 ns and is independent of the ambient gas used. This value is acceptable for laser applications.

Electron and hole transport properties in GaAs-AlGaAs superlattices

Abstract Time-resolved photoluminescence has been used to study the carrier transport in superlattice minibands (vertical transport). Transport of electrons and holes can be studied separately by using appropriate excitation densities and doping levels. Their diffusion coefficients are estimated and studied both as a function of the superlattice period and of the lattice temperature. The different behaviour of electrons and hole mobilities as a function of the SL period is evidenced. The temperature behaviour of the transport properties is similar in a superlattice and in the AlGaAs alloy with an equivalent Al concentration.

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.

High static performance GaInAs-GaInAsP SCH MQW 1.5 mu m wavelength buried ridge stripe lasers

The potential advantages of GaInAs/InP multiquantum well (MQW) structures over bulk material for improving the static properties of buried heterostructure (BH) lasers are demonstrated. Using a highly uniform metalorganic vapor phase epitaxy (MOVPE) growth, an optimized simple separate confinement heterostructure (SCH) MQW layer stack, and the buried ridge stripe (BRS) structure, improved static performances over any bulk or unstrained MQW long wavelength laser were obtained. An extremely low threshold below 2 mA was obtained in short cavity lasers, the threshold current was only 10.6 mA and 110 mW continuous-wave (CW) maximum optical power was observed using 90%/10% reflectivity coatings. >

Density-dependent transition from electron to ambipolar vertical transport in short-period GaAs-AlGaAs superlattices

Using time-resolved photoluminescence the authors have studied vertical transport in a series of superlattices with a large included 1 mu m away from the sample surface. With a streak camera, photoluminescence (PL) decays for excitation densities as low as a few 1013 cm-3 photocarriers per pulse can be recorded. At such low densities, the electrons are the minority carriers in residual p-type MBE materials. They can move without being slowed down by the holes. By varying the excitation density one is able to observe the transition from an electron transport regime to an ambipolar one. The use of a one-dimensional diffusion model for the photocreated carriers and the excitons enables one to obtain the diffusion coefficients of electrons, holes and excitons in these structures at different temperatures.

Optical characterization of the interface in GaAs/AlAs quantum wells

Luminescence, luminescence excitation as well as time resolved luminescence under resonant excitation are performed on high quality GaAs/AlAs quantum wells in order to assess the quality of the interface. The transfer from zones of a well defined thickness to zones larger by one monolayer is evidenced by selective excitation.

Stark localization in GaAs-GaAlAs superlattices under a low electric field

Abstract We show, from the photoluminescence of a GaAs-Ga 0.65 Al 0.35 As superlattice of period 70 A, that the localization of the electrons takes place at low field (∼ 1 × 10 4 V/cm). When the localization begins, the binding energy of the heavy-hole exciton is approximately the same whether the electron wavefunction is centered on the same well as the hole or on adjacent well. The model of eigenfunctions proposed by Bleuse et al. for superlattices under electric field fits our results satisfactorily. A reduction of the electric field applied to the superlattice has been obtained by using a laser beam with photon energies greater than the bandgap width of the barriers. This effect provides accurate measurements of the low field localization.

Radiative and non-radiative recombination in GaAsAlGaAs superlattices

Abstract Carrier lifetimes have been measured in MBE grown GaAsAlGaAs superlattices by time-resolved luminescence. We observed that the radiative recombination rates have comparable values in superlattices and AlGaAs alloys and that the non-radiative lifetimes are generally longer in SLs than in AlGaAs alloys.

Subnanosecond carriers lifetime measurement in 1.3μ InGaAsP

Abstract The Auger recombination coefficient has been determined in 1.3μ InGaAsP at different temperatures by observation of the luminescence decay following a 100ps pulse excitation. The Auger coefficient (Ca=2.6 10-29cm6s-1) does not increase with temperature which leads to an Auger limited T 0 value of 121K for 1.3μ InGaAsp lasers.