A. Gaarder

Ion-implanted In0.53Ga0.47As for ultrafast optoelectronic applications

Low-temperature ~LT! grown and ion-implanted GaAs have been shown to exhibit the properties ideal for ultrafast optoelectronic applications, with good carrier mobilities, high resistivities, and subpicosecond optical response times. 1,2 In this material, ionized As antisite defects act as the main electron traps and recombination centers. 3 In0.53Ga0.47As lattice matched to InP has an added interest from the point of view of optical fiber communications technology because of its large absorption at the 1.3- and 1.55-mm wavelengths. However, As antisites in InGaAs create shallow donors and, together with other intrinsic defects such as an As vacancy and a group-III ~In or Ga! interstitial, prevents fabrication of highly resistive InGaAs layers by LT growth. 4 Besides, in LT InGaAs, arsenic antisites appear in lower concentrations than in LT GaAs, therefore, subpicosecond electron lifetimes are not reached. 5,6 An electron lifetime of 400 fs was only observed in conductive LT InGaAs heavily p-doped with Be, in which the lifetime was determined by Auger recombination. 7 Ion- and proton-implanted InGaAs layers and quantum wells have shown carrier lifetimes as short as 1‐2 ps; 8,9 however, the resistivity of these

Ultrafast carrier trapping and recombination in highly resistive ion implanted InP

MeV P+ implanted and annealed p-InP, and Fe+ implanted and annealed semi-insulating InP have both been shown to produce the high resistivity, good mobility, and ultrafast optical response desired for ultrafast photodetectors. Hall effect measurements and time resolved photoluminescence were used to analyze the electrical and optical features of such implanted materials. Low temperature annealing was found to yield the fastest response times—130 fs for Fe+ implanted and 400 fs for P+ implanted InP, as well as resistivities of the order ∼106 Ω/square. It was found that the electrical activation of Fe-related centers, useful for achieving high resistivities in Fe+ implanted semi-insulating InP, was not fully realized at the annealing temperatures chosen to produce the fastest optical response. Implanting p-InP in the dose regime where type conversion occurs, and subsequent annealing at 500 °C, produces high resistivities and ultrafast carrier trapping times that are only marginally dose dependent.

Photoexcited carrier dynamics in aligned InAs/GaAs quantum dots grown on strain-relaxed InGaAs layers

Carrier dynamics in aligned InAs/GaAs quantum dots (QDs) grown on cross-hatched patterns induced by metastable InxGa1−xAs layers have been studiedby time-resolvedphotoluminescence. The low-temperature carrier lifetimes were found to be of the ord er of 100 –200 ps andd eterminedby carrier trapping andnonrad iative recombination. Comparisons with control “nonaligned” InAs QDs show remarkable di>erences in dependence of peak PL intensities on excitation power, and in PL decay times dependences on both temperature and excitation intensities. Possible origin of traps, which determine the carrier lifetimes, is discussed. ? 2003 Elsevier Science B.V. All rights reserved.

Dopant distribution in selectively regrown InP: Fe studied by time-resolved photoluminescence

We apply time-resolved photoluminescence with 1 mum spatial resolution for the characterization of iron distribution in semi-insulating InP:Fe epitaxial layers regrown by hydride vapor-phase epitaxy around etched mesas. The InP:Fe regrowth was carried out on InP:S mesas etched both along the [110] and [110] crystallographic directions, as well as on InP/InGaAsP in-plane lasers. In all cases, the Fe concentration was found to be close to the target values and showed little variation along the regrown layers.

Time-resolved micro-photoluminescence studies of deep level distribution in selectively regrown GaInP:Fe and GaAs:Fe

We apply time-resolved photoluminescence with 1-2 mum spatial resolution for the characterization of deep centre distributions in semi-insulating GaInP:Fe and GaAs:Fe epitaxial layers regrown by hy ...

Ultrafast carrier dynamics in highly resistive InP and InGaAs produced by ion implantation

Heavy ion implantation into InP and In0.53Ga0.47As and rapid thermal annealing has been applied to produce materials with high resistivity, good mobility and ultrashort carrier lifetime, as required for ultrafast optoelectronic applications. Two implantation methods have been analyzed: Fe+ implantation into semi-insulating InP and InGaAs, and P+ implantation into p-doped InP and InGaAs. Both approaches allow production of layers with high sheet resistance, up to 106 Ω/square for the P+-implanted compounds. Electron mobility in the high resistivity layers is of the order of 102 cm2V-1s-1. Carrier lifetimes, measured by the time-resolved photoluminescence and reflectivity, can be tuned from ~100 femtoseconds to tens of picoseconds by choosing implantation and annealing conditions. Measurements of carrier dynamics have shown that carrier traps act as efficient recombination centers, at least for the case of InP. The dependencies of electrical and ultrafast optical properties on the implantation dose and annealing temperature are determined by the interplay between shallow P and As antisite-related donors, deep Fe-related acceptors and defect complexes.

Carrier dynamics in spatially ordered InAs quantum dots

Spatial ordering of InAs quantum dots was attained by using misfit dislocations generated in a metastable InGaAs layer by means of thermal annealing. Influence of quantum dot positional ordering and dot proximity to dislocation arrays on carrier dynamics was studied by timeresolved photoluminescence. Substantially narrower inhomogeneous broadening from the ordered quantum dots was observed. Excitation intensity dependence of the photoluminescence intensity and carrier lifetime indicates stronger influence of nonradiative recombination for the ordered quantum dot structures. Numerical simulations allow estimating electron and hole capture rates from the quantum dots to traps located either at the quantum dot interfaces or in the vicinity of the quantum dots.

Dopant distribution in selectively regrown InP:Fe and InGaP:Fe studied by time-resolved photoluminescence

Time resolved photoluminescence with 1-2 /spl mu/m spatial resolution has been applied for characterization of iron distribution in semi-insulating InP and InGaP epitaxial layers regrown by hydride vapor phase epitaxy around etched mesas. The mesas for the InP regrowth were etched along [110] and [-110]. For InGaP they contained GaAs/AlGaAs quantum well laser structures. In all cases, the Fe concentration was found to be close to the target values and showed little variation along the regrown layers.

Ultrafast carrier trapping and recombination in high resistivity ion implanted InP

MeV P/sup +/ implanted and annealed p-InP and Fe/sup +/ implanted and annealed semi-insulating InP have both been shown to produce the high resistivity, good mobility and ultrafast optical response desired for ultrafast photodetectors. Low temperature annealing was found to yield the fastest response times-130 fs for Fe/sup +/ implanted and 400 fs for P/sup +/ implanted InP, as well as resistivities of the order of 10/sup 6//spl Omega//square. For devices, the most advantageous treatment is implanting p-InP with P/sup +/ in the dose regime where type conversion occurs, with subsequent annealing at 500/spl deg/C. This produces high resistivities and ultrafast carrier trapping times that are only marginally dose dependent.

Ultrafast carrier dynamics in self-assembled semiconductor quantum dots

Carrier transfer into quantum dots has been investigated by time-resolved photoluminescence spectroscopy in sets of InGaAs/GaAs quantum dot samples with gradually changing interband transition and intraband level energies, and quantum dot density. Efficient electron relaxation by LO phonon emission has been observed for samples in which the electron energy level separation was close to the LO phonon energy. At higher photoexcited carrier densities, carrier-carrier scattering is found to be the most efficient relaxation mechanism leading to picosecond and subpicosecond carrier transfer times. The rate of carrier transfer into the dots was also found to increase with increased quantum dot density. For the low quantum dot density structures carrier transfer is inhibited by potential barriers at the barrier/quantum dot interfaces.