We report temperature-dependent time-integrated and time-resolved photoluminescence (PL) studies of InGaN/GaN multiple quantum wells (MQWs) grown by metalorganic chemical vapor deposition. observed anomalous emission behavior, specifically an S-shaped (decrease–increase–decrease) temperature dependence the peak energy (Ep) for InGaN-related PL with increasing temperature: Ep redshifts in range 10–70 K, blueshifts 70–150 again 150–300 K temperature. In addition, when redshifts, spectral width...

Optically pumped near ultraviolet lasing from single-crystal GaN grown by metalorganic chemical vapor deposition has been achieved over a temperature range 10 K to 375 using side-pumping geometry on small barlike samples. The laser emission threshold was measured as function of and the found show weak dependence: ∼500 kW/cm2 at ∼800 room (295 K) for one particular sample studied. longitudinal modes were clearly observed. characteristics dependence suggests that is suitable material...

We present the results of optical studies properties InxGa1−xN epitaxial layers (0<x<0.2) grown by metalorganic chemical vapor deposition. The effects alloying on fundamental band gap were investigated using a variety spectroscopic techniques. band-gap energies alloys determined photomodulation spectroscopy measurements and variation was measured as function temperature. pressure for samples with different alloy concentrations examined studying shift photoluminescence (PL)...

Optical absorption measurements were performed on a series of thin GaN epilayers. Sharp spectral features observed due to the 1s A and B exciton transitions. Using polarization dependent absorption, C transition was identified. broad feature at ∼3.6 eV, which is attributed indirect exciton-phonon absorption. The excitonic structure found persist well above room temperature. fit Varshni formula yielded temperature dependence E(T)=E(T=0)−11.8×10−4T2(1414+T) eV for excitons. linewidth studied...

We present a comprehensive study of the optical characteristics ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{N}\mathrm{}$ epilayers $(0<~x<~0.6)$ by means photoluminescence (PL), PL excitation, and time-resolved spectroscopy. For with large Al content, we observed an anomalous temperature dependence: (i) ``S-shaped'' peak energy shift (decrease-increase-decrease) (ii) ``inverted S-shaped'' spectral width broadening (increase-decrease-increase) increasing temperature. that...

We have systematically studied the influence of Si doping on characteristics InGaN/GaN multiple quantum wells (MQWs) by means high-resolution x-ray diffraction (HRXRD), photoluminescence (PL), PL excitation (PLE), and time-resolved spectroscopy. The twelve- period MQWs were grown metalorganic chemical vapor deposition. in GaN barriers was varied from 1×1017 to 3×1019 cm−3. Information structural quality as a function extracted linewidth broadening higher-order superlattice satellite peaks...

Laser action was observed in GaN pyramids under strong optical pumping at room temperature. The were laterally overgrown on a patterned GaN/AlN seeding layer grown (111) silicon substrate by metal–organic chemical vapor deposition. Each pyramid had 15-μm-wide hexagonal base and average 15 μm height. individually pumped, imaged, spectrally analyzed through high-magnification telescope system using high-density pulsed excitation source. Under high levels of pumping, multimode laser temperature...

Nanobubbles, when dispersed in a liquid phase, may enhance mass transport, adsorption, and reactions many industrial applications, such as fabrication of functional materials, drug delivery, water treatment, carbon dioxide capture, surface decontamination. Here, we experimentally study the early time spreading dynamics nanobubble-laden surfactant drops on hydrophilic solid submerged an oil phase. Along with recovering retarding effects surfactants wetting dynamics, report that nanobubbles...

We study the impact of spacetime quantum fluctuation on thermodynamics Reissner–Nordström anti-de Sitter (RN-AdS) black hole immersed in Perfect Fluid Dark Matter (PFDM). First, we add RN-AdS PFDM and write metric, which effect is reflected by a parameter a. For quantum-corrected hole, discover existence minimum horizon radius a, also known as remnant radius. Next, establish validity generalized Smarr relation analyze phase transition hole. find similarities with van der Waals gas when far...

We report the results of an experimental study on near-threshold gain mechanisms in optically pumped GaN epilayers temperature range 20–700 K. High-quality single-crystal films grown 6H–SiC and (0001) sapphire were used this study. show that dominant mechanism is inelastic exciton–exciton scattering for temperatures below ∼150 K, characterized by band-filling phenomena a low stimulated emission (SE) threshold. An analysis both dependence SE threshold relative shift between band-edge-related...

Femtosecond degenerate four-wave-mixing (FWM) is used to study coherent dynamics of excitons in GaN epilayers. Spectrally resolved (SR) FWM data are dominated by the $A$ and $B$ intrinsic excitonic resonances. SR combined with time-integrated (TI) demonstrates that resonances nearly homogeneously broadened even at low temperature. The temperature-dependent dephasing rate deduce exciton-phonon interaction rates. TI shows a strong beating between beats shown be true quantum beats. In addition,...

We have systematically studied both the spontaneous and stimulated emission properties in blue-light-emitting ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{N}/\mathrm{G}\mathrm{a}\mathrm{N}$ multiple quantum well structures using various linear nonlinear optical techniques. Our experimental observations are consistently understandable context of localization carriers associated with large potential fluctuations...

The carrier recombination dynamics in a series of ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{N}/\mathrm{G}\mathrm{a}\mathrm{N}$ multiple quantum wells, nominally identical apart from different Si doping concentrations the GaN barriers, was studied by time-resolved photoluminescence (PL) with excitation densities ranging $220 {\mathrm{n}\mathrm{J}/\mathrm{c}\mathrm{m}}^{2}$ to $28 \ensuremath{\mu}{\mathrm{J}/\mathrm{c}\mathrm{m}}^{2}$ at 10 K and 300 K. At early time delays...

Stimulated emission (SE) in optically pumped InGaN/GaN multiquantum well (MQW) structures grown by metalorganic chemical vapor deposition was experimentally studied the temperature range of 175–575 K. The GaN barriers were intentionally doped with a different Si concentration ranging from 1×1017 to 3×1019 cm−3 and effects doping on optical properties MQWs investigated. SE threshold measured as function compared bulk GaN. We observed that had low value weak dependence: for example, ∼25 kW/cm2...

We present the results of optical studies on properties GaN grown by low-pressure metalorganic chemical-vapor deposition, with emphasis issues vital to device applications such as stimulated emission and laser action well carrier relaxation dynamics. By pumping, lasing were investigated over a wide temperature range up 420 K. Using picosecond streak camera, free bound exciton decay times examined. In addition, effects pressure interband transitions associated impurity/defect states studied...

We have studied laser action of ZnSe and ZnS0.05Se0.95 samples grown by seeded physical vapor phase transport (SPVT) technique in the near resonant two-photon absorption regime. The pumped lasing was observed using a tunable near-infrared nanosecond (830–890 nm). Blue could be up to 200 K threshold measured ∼7 MW/cm2 at 10 K. This work demonstrates applicability diode lasers as pumping sources excite ZnSe-based materials. By comparing energy position with that one-photon examining red shift...

Optically pumped stimulated emission (SE) from InGaN/GaN multiple quantum wells (MQWs) grown by metalorganic chemical vapor deposition has been systematically studied as a function of excitation photon energy (Eexc) to further understand the origin SE in these structures. was observed for energies well below that absorption edge MQWs, indicating states responsible soft structures can efficiently couple carriers with gain region. “Mobility edge”-type behavior peak Eexc varied. The effective...

We have studied the structural and optical properties of InxGa1−xN/GaN multiple quantum wells with different In compositions 8.8%, 12.0%, 13.3% by means high-resolution x-ray diffraction (HRXRD), photoluminescence (PL), PL excitation (PLE), stimulated emission (SE), time-resolved spectroscopy. As composition increases, superlattice peaks in HRXRD measurements PLE band edge broaden, indicating deterioration interface quality due to difficulty uniform incorporation into GaN layer. However,...

We report the structural properties of InGaN/GaN/AlGaN multiple quantum wells (MQWs) by means two-dimensional reciprocal space mapping (RSM) high resolution x-ray diffraction. The influence Si doping in GaN barriers on characteristics has been studied for 12-period MQWs grown metalorganic chemical vapor deposition, which have different concentrations ranging from 1×1017 to 3×1019 cm−3. Information quality these was extracted linewidth broadening higher-order superlattice satellite peaks, as...

Nanosecond nondegenerate optical pump-probe experiments have been performed on InGaN thin films and InGaN/GaN multiple quantum wells. Bleaching of absorption the localized band tail states was observed with increasing excitation density (Iexc) pump pulse. The dynamics bleaching found to depend localization depth Iexc. With high Iexc, large blueshifts in spontaneous emission luminescence peaks were also observed, magnitude which again states. Stimulated is from samples Iexc correlates...

Photoluminescence spectra of cubic GaN grown on a GaAs substrate by molecular beam epitaxy have been studied as function hydrostatic pressure at 10 K. The are abundant in emission structures arising from variety radiative recombination processes, such free-electron–bound-hole and donor-acceptor pair transitions. These peaks shift to higher energy with increasing pressure, providing measure the coefficient band gap GaN. In addition, spectral feature, which is superimposed other not observable...