Saulius Marcinkevicius

GaBiAs: A material for optoelectronic terahertz devices

GaBiAs layers have been grown by molecular beam epitaxy at low (270–330°C) temperatures and were characterized by several experimental techniques. It was shown that the spectral photosensitivity cutoff wavelength reaches ∼1.4μm when the growth temperature is as low as 280°C. Optical pump–terahertz probe measurements made on these layers have evidenced that the electron trapping time decreases with decreasing growth temperature from 20 to about 1ps. GaBiAs layers were used for manufacturing photoconductive terahertz emitters and detectors, which, when excited with Ti:sapphire laser pulses, have demonstrated a signal bandwidth of 3THz.

1 micron wavelength photo- and electroluminescence from a conjugated polymer

We report photo- and electroluminescence from an alternating conjugated polymer consisting of fluorene units and low-band gap donor-acceptor-donor (D–A–D) units. The D–A–D segment includes two elec ...

Transient electromagnetically induced transparency in self-assembled quantum dots

A coherent absorption dip in pump-probe experiment performed on a ten layer optically thin InGaAs/GaAs quantum dot (QD) structure has been observed. Measurements performed for different wavelengths ...

Picosecond carrier lifetime in GaAs implanted with high doses of As ions: An alternative material to low‐temperature GaAs for optoelectronic applications

Nonstoichiometric GaAs obtained by implantation with 2 MeV arsenic ions at 1015 cm−2 dose is studied. As‐implanted samples show a <200 fs lifetime of photocarriers and low resistivity due to hopping, with mobility less than 1 cm2/V s. Annealing of the samples at 600 °C leads to substantial recovery of postimplant damage, as seen from Rutherford backscattering channeling spectra and mobility increase to about 2000 cm2/V s, but photocarrier lifetime is still about 1 ps. These parameters are similar to those of low‐temperature GaAs annealed at 600 °C, and make arsenic implanted GaAs an interesting material for optoelectronic applications.

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

Localization potentials in AlGaN epitaxial films studied by scanning near-field optical spectroscopy

Scanning near-field photoluminescence spectroscopy has been applied to evaluate bandgap fluctuations in epitaxial AlGaN films with the AlN molar fraction varying from 0.30 to 0.50. A dual localizat ...

Mode locking a 1550 nm semiconductor disk laser by using a GaInNAs saturable absorber

Passive mode locking of an optically pumped, InP-based, 1550 nm semiconductor disk laser by using a GaInNAs saturable absorber mirror is demonstrated. To reduce material heating and enable high-power operation, a 50 microm thick diamond heat spreader is bonded to the surface of the gain chip. The laser operates at a repetition frequency of 2.97 GHz and emits near-transform-limited 3.2 ps pulses with an average output power of 120 mW.

Time-resolved analysis of the white photoluminescence from SiO2 films after Si and C coimplantation

The analysis of the white photoluminescence (PL) from Si+ and C+ coimplanted SiO2 is reported as a function of the implanted dose. By both steady and time-resolved measurements, the presence of sev ...

High current-induced degradation of AlGaN ultraviolet light emitting diodes

Degradation under high current stress of AlGaN quantum well based light emitting diodes emitting at 285 and 310 nm has been studied using electroluminescence, time-resolved photoluminescence and current-voltage experimental techniques. The measurements have revealed that during aging decrease of the emission intensity is accompanied by increase of the tunneling current, increase of the nitrogen vacancy concentration and partial compensation of the p-doping. The main role in the device degradation has been ascribed to formation of tunneling conductivity channels, probably, via activation of the closed core screw dislocations with the help of nitrogen vacancies. Carrier lifetimes in the quantum wells and the p-cladding were found to be unaffected by the aging process, suggesting that the nonradiative recombination has a lesser influence on the device degradation.

Ultrafast carrier trapping in Be-doped low-temperature-grown GaAs

Time-resolved photoluminescence is used to study low-temperature-grown (LTG) GaAs with Be doping. It is observed that the carrier trapping time in the as-grown LTG GaAs increases with Be doping. Similar effect is observed also in the annealed samples doped with less than 3×1019 cm−3 of Be. At higher doping levels, the trapping time in these samples is abruptly reduced to below 100 fs. This behavior is attributed to changes in As antisite density and the compensation effect of Be.