We have investigated by temperature-dependent photoluminescence (PL) spectroscopy as-grown GaInNAs, InGaAs, and GaAsN quantum wells (QWs) embedded in a GaAs matrix. The evolution of the PL peak position and of the PL linewidth shows evidence of a strong carrier localization for the GaInNAs QWs only. The high delocalization temperature, in the 150 K range, indicates the presence of a high density of possibly deep-localizing potential wells. In addition, a higher density of nonradiative recombination centers appears to result in stronger carrier localization. Transmission electron microscopy reveals well defined, flat interfaces, in these comparatively high N-content (yN∼0.04–0.05) QWs. Our results thus demonstrate that the origin of localization in GaInNAs QWs is the concomitant presence of both In and N, which may result in strain and/or composition fluctuations.

We have investigated by photoluminescence spectroscopy and x-ray diffraction the influence of ex situ postgrowth annealing on the properties of a series of dedicated Ga(In)(N)As ternary and quaternary quantum wells (QWs) confined by various barrier layers. We show that the low growth temperature and not N per se, is largely responsible for the low radiative efficiency of Ga(In)NAs QWs. Furthermore, postgrowth annealing induces a blueshift of the photoluminescence line in the case of quaternary GaInNAs QWs only, while x-ray diffraction reveals the absence of compositional change. We conclude with the occurrence of a local reorganization of the N-bonding configuration within the GaInNAs quaternary material during annealing.

The impact of rapid thermal annealing on the optical emission of GaInNAs/GaAs quantum wells (QWs) grown by molecular beam epitaxy with high In and N content is shown to be highly dependent on the crystal structure of the QWs, as determined by transmission electron microscopy. Due to the presence of higher concentrations of nonradiative recombination centers, the annealing temperature required to obtain maximum photoluminescence emission is higher for the QW with strong structural modulation of the upper interface [at the onset of three-dimensional (3D) growth], intermediate for the two-dimensional (2D) grown QW with compositional fluctuations, and lower for the homogeneous 2D grown QW. Moreover, the transition from homogeneous 2D growth, to 2D growth with compositional fluctuations, and finally 3D growth, leads to progressively deeper carrier localization states below the conduction-band edge. Increasing annealing temperatures gradually shifts the localization states closer to the conduction-band edge, predominantly when compositional fluctuations are present. These results suggest a link between the formation of carrier localization centers and the presence of alloy fluctuations along the QW.

No abstract

Until now, phosphorus is the best substitutional dopant for n‐type diamond. Its incorporation is usually achieved using phosphine gas. However, organic precursors of phosphorus have been recently investigated. Among them, tertiarybutylphosphine (TBP) appears as an alternative to phosphine. In this report, we investigate the n‐type doping of diamond with liquid TBP using the metal‐organic chemical vapour deposition (MOCVD) technology for dopant incorporation. Our first results with liquid TBP precursor are compared with the results published for gaseous organic precursors of phosphorus. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

In n-type diamond doped with phosphorus, exciton properties have been investigated by cathodoluminescence as a function of the phosphorus concentration and the temperature. The homoepitaxial diamond layers were grown by microwave plasma-assisted chemical vapor deposition and doped using a liquid organic precursor of phosphorus (tertiarybutylphosphine). The phosphorus concentration ranges from 5.2×1016 to 3.3×1018 cm−3 as measured by secondary ion mass spectrometry. It is shown that the ratio between the luminescence intensities of the neutral phosphorus-bound exciton and the free exciton follows the dopant concentration. Calibration graphs are presented to determine the phosphorus contents in diamond using cathodoluminescence spectroscopy.

We have investigated the influence of both the growth rate and the growth temperature on the structural and optical properties of GaAs0.972N0.028/GaAs single quantum wells grown by solid-source molecular beam epitaxy. The results are analyzed in light of the surface phase diagram obtained from in situ reflection high energy electron diffraction. We show that the best quality is achieved at the highest temperature below the onset of alloy decomposition. The use of high growth rates allows one to significantly increase the growth temperature. Our results demonstrate that it is the GaAsN alloy stability which governs the sample properties.

We investigated the influence of the growth temperature (Tgr) on the microstructure and on the optical properties of GaInNAs quantum wells (QWs). By comparing the structural information (transmission electron microscopy) with the optical properties (photoluminescence spectroscopy), we demonstrate that high photoluminescence efficiency of GaInNAs QWs is achieved only when the two-dimensional growth mode is preserved, which can be obtained at a low Tgr even for high In content. We also show composition modulations in the GaInNAs QWs, which can lead to the interface roughness.