On Oscillating Carrier Dynamics in Highly Excited InP:Fe Crystals

The numerical analysis and experimental data on time-resolved four-wave mixing confirmed a novel origin of oscillations in subnanosecond carrier dynamics in highly excited InP:Fe crystals. The effect was attributed to simultaneous presence of electron and hole gratings, which drift in the space charge field and contribute constructively or destructively to refractive index modulation in time domain

Investigation of Carrier Recombination in Si Heavily Irradiated by Neutrons

Variations of recombination lifetime, with fluence of the reactor neutrons from $10^{12}$ to $3×10^{16} n//cm^2$, in the magnetic field applied Czochralski grown Si samples are examined by the contactless transient techniques of the microwave probed photoconductivity and dynamic gratings. A nearly linear decrease in lifetime from few microseconds to about 200 ps within the examined range of neutron irradiation fluences was obtained. This dependence persists under relatively low (≤80°C) temperature heat treatments. Also, cross-sectional scans of lifetime depth-profiles were examined, which show rather high homogeneity of lifetime values within wafer thickness

Investigation of Carrier Recombination in Si Heavily Irradiated by Neutrons

Variations of recombination lifetime, with fluence of the reactor neutrons from $10^{12}$ to $3×10^{16} n//cm^2$, in the magnetic field applied Czochralski grown Si samples are examined by the contactless transient techniques of the microwave probed photoconductivity and dynamic gratings. A nearly linear decrease in lifetime from few microseconds to about 200 ps within the examined range of neutron irradiation fluences was obtained. This dependence persists under relatively low (≤80°C) temperature heat treatments. Also, cross-sectional scans of lifetime depth-profiles were examined, which show rather high homogeneity of lifetime values within wafer thickness

Optical investigation of non-equilibrium carrier dynamics in differently doped VGF-grown ZnTe single crystals

We applied a time-resolved FWM technique to study the dynamics of photoexcited carriers in differently doped VGF-grown ZnTe crystals at room temperature. We observed a fast carrier trapping to deep levels in phosphorus doped and undoped samples. The measurements at below and above band-gap excitations revealed the much higher concentration of these levels near the surface than in the bulk in both samples. The concentration of deep traps has been estimated for phosphorus doped sample N=(1-2)e15 cm–3 in the bulk and N=(3-5)e18 cm–3 near the surface. In the undoped sample these traps are present at much higher concentration. The electron and hole mobilities µn=(500±28) cm2/Vs and µh=(16±6) cm2/Vs were estimated from the measured diffusion coefficient values D=(12.5±0.7) cm2/s in the p-type sample and D=(0.8±0.3) cm2/s in the semi-insulating one

Study of carrier recombination transient characteristics in MOCVD grown GaN dependent on layer thickness

The MOCVD grown GaN epi-layers of different thickness have been examined in order to clarify a role of surface recombination, to separate an impact of radiative and non-radiative recombination and disorder factors. The microwave probed –photoconductivity (MW-PC) and spectrally resolved photo-luminescence (PL) transients were simultaneously recorded under ultraviolet (UV) light 354 nm pulsed 500 ps excitation. The MW-PC transients exhibited the carrier decay components associated with carrier decay within micro-crystals and the disordered structure on the periphery areas surrounding crystalline columns. Three PL bands were resolved within PL spectrum, namely, the exciton ascribed UV-PL band edge for hν>3.3 eV, blue B-PL band for 2.5 < hν < 3.0 eV and yellow Y-PL band with hν < 2.4 eV. It has been obtained that intensity of UV-PL band increases with excitation density, while intensity of B-PL band is nearly invariant. However, intensity of the Y-PL increases with reduction of the excitation density. The Y-PL can be associated with trapping centers. A reduction of UV excitation density leads to a decrease of the relative amplitude of the asymptotic component within the MW-PC transients and to an increase of the amplitude as well as duration of the yellow spectral band (Y-PL) asymptotic component. Fractional index α with values 0.5 < α < 0.8 was evaluated for the stretched-exponent component which fits the experimental transients determined by the disordered structure ascribed to the periphery areas surrounding the crystalline columns

Fabrication and replication of micro-optical structures for growth of GaN-based light emitting diodes

Abstract not reproduced here by request of the publisher. The text is available from: http://dx.doi.org/10.1117/12.203370