We report the observation of optically pumped lasing in ZnO at room temperature. Thin films of ZnO were grown by plasma-enhanced molecular beam epitaxy on (0001) sapphire substrates. Laser cavities formed by cleaving were found to lase at a threshold excitation intensity of 240 kW cm−2. We believe these results demonstrate the high quality of ZnO epilayers grown by molecular beam epitaxy while clearly demonstrating the viability of ZnO based light emitting devices.

Optically pumped lasing of ZnO at room temperature

The synthesis, crystal growth, and structural and optoelectronic characterization has been carried out for the perovskite compound CsPbBr3. This compound is a direct band gap semiconductor which meets most of the requirements for successful detection of X- and γ-ray radiation, such as high attenuation, high resistivity, and significant photoconductivity response, with detector resolution comparable to that of commercial, state-of-the-art materials. A structural phase transition which occurs during crystal growth at higher temperature does not seem to affect its crystal quality. Its μτ product for both hole and electron carriers is approximately equal. The μτ product for electrons is comparable to cadmium zinc telluride (CZT) and that for holes is 10 times higher than CZT.

Crystal Growth of the Perovskite Semiconductor CsPbBr3: A New Material for High-Energy Radiation Detection

We present a comprehensive review of the material properties of cadmium zinc telluride (CZT, Cd1ˇxZnxTe) with zinc content xa 0:1‐0.2. Particular emphasis is placed on those aspects of this material related to room temperature nuclear detectors. A review of the structural properties, charge transport, and contacting issues and how these are related to detector and spectrometer performance is presented. A comprehensive literature survey and bibliography are also included. # 2001 Elsevier Science B.V. All rights reserved.

Cadmium zinc telluride and its use as a nuclear radiation detector material

Relativistic interaction of short-pulse lasers with underdense plasmas has recently led to the emergence of a novel generation of femtosecond x-ray sources. Based on radiation from electrons accelerated in plasma, these sources have the common properties to be compact and to deliver collimated, incoherent, and femtosecond radiation. In this article, within a unified formalism, the betatron radiation of trapped and accelerated electrons in the so-called bubble regime, the synchrotron radiation of laser-accelerated electrons in usual meter-scale undulators, the nonlinear Thomson scattering from relativistic electrons oscillating in an intense laser field, and the Thomson backscattered radiation of a laser beam by laser-accelerated electrons are reviewed. The underlying physics is presented using ideal models, the relevant parameters are defined, and analytical expressions providing the features of the sources are given. Numerical simulations and a summary of recent experimental results on the different mechanisms are also presented. Each section ends with the foreseen development of each scheme. Finally, one of the most promising applications of laser-plasma accelerators is discussed: the realization of a compact free-electron laser in the x-ray range of the spectrum. In the conclusion, the relevant parameters characterizing each sources are summarized. Considering typical laser-plasma interaction parameters obtained with currently available lasers, examples of the source features are given. The sources are then compared to each other in order to define their field of applications.

https://hal.archives-ouvertes.fr/hal-01164031/document

Femtosecond x rays from laser-plasma accelerators

Provided is a light emitting diode (LED) manufactured by using a wafer bonding method and a method of manufacturing a LED by using a wafer bonding method. The wafer bonding method may include interposing a stress relaxation layer (33) formed of a metal between a semiconductor layer (20) and a bonding substrate (31). When the stress relaxation layer is used, stress between the bonding substrate and a growth substrate may be offset due to the flexibility of metal, and accordingly, bending or warpage of the bonding substrate may be reduced or prevented.

Light-emitting device and method of manufacturing the same

We have studied the optical response of ZnSe in the 1.5--5.3-eV photon-energy range at room temperature by spectroscopic ellipsometry. The measured dielectric-function spectra reveal distinct structures at energies of the ${\mathit{E}}_{0}$, ${\mathit{E}}_{0}$+${\mathrm{\ensuremath{\Delta}}}_{0}$, ${\mathit{E}}_{1}$, and ${\mathit{E}}_{1}$+${\mathrm{\ensuremath{\Delta}}}_{1}$ critical points (CP's). These data are analyzed on the basis of a simplified model of the interband transitions. The ${\mathit{E}}_{0}$-(${\mathit{E}}_{0}$+${\mathrm{\ensuremath{\Delta}}}_{0}$) structures are characterized by a three-dimensional ${\mathit{M}}_{0}$ CP, the ${\mathit{E}}_{1}$-(${\mathit{E}}_{1}$+${\mathrm{\ensuremath{\Delta}}}_{1}$) structures by a two-dimensional ${\mathit{M}}_{0}$ CP, and the ${\mathit{E}}_{2}$ structure by a classical Lorentzian oscillator (damped harmonic oscillator). The experimental data could not be explained within the framework of the one-electron approximation, since excitonic effects may profoundly modify the CP singularity structure. The model is thus made to account for the excitonic effects at these CP's; our results are in satisfactory agreement with the experiment over the entire range of photon energies. Dielectric-function-related optical constants of ZnSe, such as the refractive index, the extinction coefficient, and the absorption coefficient, are also presented and analyzed.

Optical properties of ZnSe

The photoluminescent properties of free and bound excitons in high-purity p- and n-type CdTe single crystals are investigated in detail in connection with the dependence on excitation intensity, temperature, impurity-doping, and uniaxial stress. Intense free-exciton emission is observed in the single crystals grown from solutions and vapor epitaxial methods. From the thermal dissociation processes and the analysis on the basis of the effective mass argument developed by Sharma and Rodriguez and by Hopfield, an assignment of exciton emission lines is tried.



Die Photolumineszenz freier und gebundener Exzitonen in hochreinen p- und n-leiten-den CdTe-Einkristallen wird ausfuhrlich mit der Abhangigkeit von Anregungsintensitat, Temperatur, Storstellendotierung und uniaxialer Spannung untersucht. In Einkristallen aus Losungen und mit epitaktischen Methoden aus der Dampfphase wird eine intensive Emission freier Exzitonen beobachtet. Aus dem thermischen Dissoziationsprozes und der Analyse auf der Grundlage effektiver Massen nach Sharma und Rodriguez sowie Hopfield wird eine Zuordnung der Exzitonen-Emissionslinien angegeben.

Tsunemasa Taguchi

Papers

Optical properties of ZnSe

Excitonic emission in cadmium telluride

Excitonic and edge emissions in MOCVD-grown ZnS films and ZnSe-ZnS superlattices☆

A new 1.47 eV defect-luminescence band in MOCVD-grown CdTe on (100) GaAs

Growth of high-purity ZnSe by sublimation THM and the characteristics of the Y and Z deep-level emission lines