High-indium-content InxGa1-xAs/GaAs quantum wells with emission wavelengths above 1.25 mu m at room temperature

High-indium-content InxGa1-xAs/GaAs single/multi-quantum well (SQW/MQW) structures have been systematically investigated. By optimizing the molecular-beam epitaxy growth conditions, the critical thickness of the strained In0.475Ga0.525As/GaAs QWs is raised to 7 nm, which is much higher than the value given by the Matthews and Blakeslee model. The good crystalline quality of the strained InGaAs/GaAs MQWs is proved by x-ray rocking curves. Photoluminescence measurements show that an emission wavelength of 1.25 mum at room temperatures with narrower full width at half maximum less than 30 meV can be obtained. The strain relaxation mechanism is discussed using the Matthews-Blakeslee model. (C) 2004 American Institute of Physics.

Influence of Mg content on molecular-beam-epitaxy-grown ZnMgS ultraviolet photodetectors

Zn1-xMgxS-based Schottky barrier ultraviolet (UV) photodetectors were fabricated using the molecular-beam-epitaxy (MBE) technique. The influence of Mg content on MBE-grown Zn1-xMgxS-based UV photodetectors has been investigated in details with a variety of experimental techniques, including photoresponse (PR), capacitance-voltage, deep level transient Fourier spectroscopy (DLTFS) and photoluminescence (PL). The room-temperature PR results show that the abrupt long-wavelength cutoffs covering 325, 305 295. and 270 nm with Mg contents of 16%, 44%, 57%, and 75% in the Zn1-xMgxS active layers, respectively, were achieved. But the responsivity and the external quantum efficiency exhibited a slight decrease with the Mg content increasing. In good agreement with the PR results, both of the integrated intensity of the PL spectra obtained from Zn1-xMgxS thin films with different Mg compositions (x = 31% and 52%, respectively) and the DLTFS spectra obtained from Zn1-xMgxS-based (x = 5% and 45%, respectively) UV photodetector samples clearly revealed a significant concentration increase of the non-radiative deep traps with increasing Mg containing in the ZnMgS active layers. Our experimental results also indicate that the MBE-grown ZnMgS-based photodetectors can offer the promising characteristics for the detection of short-wavelength UV radiation. (C) 2004 Elsevier B.V. All rights reserved.

High structural and optical quality 1.3 mu m GaInNAs/GaAs quantum wells with higher indium content grown by molecular-beam expitaxy

High structural and optical quality 1.3 mu m GaInNAs/GaAs quantum well (QW) samples with higher (42.5%) indium content were successfully grown by molecular-beam epitaxy. The cross-sectional transmission electron microscopy measurements reveal that there are no structural defects in such high indium content QWs. The room-temperature photoluminescence peak intensity of the GaIn0.425NAs/GaAs (6 nm/20 nm) 3QW is higher than, and the full width at half maximum is comparable to, that of In0.425GaAs/GaAs 3QW, indicating improved optical quality caused by strain compensation effect of introducing N to the high indium content InGaAs epilayer. (C) 2005 American Institute of Physics.

The effect of In content on high-density InxGa1-xAs quantum dots

We have successfully grown self-assembled InxGa1-xAs (x = 0.44, 0.47, 0.50) quantum dots (QDs) with high density (> 10(11)/cm(2)) by MBE. The effect of In content on the high-density QD is investigated by atomic force microscopy (AFM) and photoluminescence (PL) spectra. It is found that sample with In-mole-fraction of 0.5 shows small size fluctuation and high PL intensity. The influence of growth temperature on high-density QD is also investigated in our experiment. (c) 2005 Elsevier B.V. All rights reserved.

Room temperature 1.25 mu m emission from high indium content InxGa1-xAs/GaAs quantum wells grown by molecular beam epitaxy

Long-wavelength high indium content InxGa1-xAs/GaAs single/multi quantum wells (QWs) structures have been successfully grown by molecular beam epitaxy. It is evidenced by X-ray measurements that the critical thickness of the well width of InxGa1-xAs/GaAs QWs with an indium content x of 47.5% can be raised up to 7nm without strain relation. 1.25μ m photoluminescence (PL) emission is obtained from the QWs with narrower full-width at half maximum (FWHM) less than 30meV. Our results are important basements which are useful for further fabricating GaAs-based long-wavelength devices. © 2005 Elsevier B.V. All rights reserved.

Characteristics of high Al content AlxGa1-xN grown by metalorganic chemical vapor deposition

The epitaxial growth of AlxGa1-xN film with high Al content by metalorganic chemical vapor deposition (MOCVD) has been accomplished. The resulting Al content was determined to be 54% by high resolution X-ray diffraction (HRXRD) and Vegard's law. The full width at half maximum (FWHM) of the AlGaN (0002) HRXRD rocking curve was about 597 arcsec. Atomic force microscopy (AFM) image showed a relatively rough surface with grain-like islands, mainly coming from the low surface mobility of adsorbed Alspecies. From transmittance measurement, the cut-off wavelength was around 280 nm and Fabry-Perot fringes were clearly visible in the transmission region. Cathodoluminescence (CL) measurement indicated that there existed a uniformity in the growth direction and a non-uniformity in the lateral direction. (C) 2007 Elsevier Ltd. All rights reserved.