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Dependence of electronic properties on nitrogen concentration in GaAs 1− x N x dilute alloys

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Abstract

Based on the pseudopotential scheme, the effect of nitrogen concentration on electronic properties of zinc-blende GaAs1−xNx alloys has been investigated for small amounts of N. The agreement between our calculated electronic band parameters and the available experimental data is generally reasonable. In agreement with recent experiment, we find that the incorporation of a few percent of N in the material of interest reduces substantially the fundamental band-gap energy and narrows the full valence band width. The electron and heavy hole effective masses are found to decrease rapidly when adding a concentration of nitrogen less than 0.005 in GaAs. This may increase the mobility of electrons and heavy holes providing new opportunities regarding the transport properties. The information derived from the present study shows that GaAs1−xNx (0⩽x⩽0.05) properties may have an important optoelectronic applications in infrared and mid-infrared spectral regions.

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... III-V dilute nitride alloys such as GaAs 1−x N x , GaSb 1−x N x , etc. obtained by incorporating a small fraction (generally less than 5%) of nitrogen into III-V binary compounds such as GaAs, GaSb, InAs, etc. are highly important for the fabrication of near-infrared optoelectronic devices [1][2][3][4][5][6]. These dilute systems have sparked a great interest and have been extensively studied over the two last decades [7][8][9][10][11]. This is because of their uncommon physical properties. ...
... This is because of their uncommon physical properties. In particular, their band gap energy is drastically reduced as more N-atoms are inserted [7,8] into the host material. The strong reduction of the gap is the consequence of the strong parameter of curvature (optical bowing parameter) that has been experimentally observed for some dilute nitrides such as GaPN [7,12,13], InPN [14,15] and GaAsN [7,[16][17][18]. ...
... It is worth noting that the N composition x = 0.03 is an experimentally realistic value as reported in Refs. [7,8]. Besides, our quantum well is a stained one because of the difference between the lattice parameters of the well layer (GaAs 0.97 N 0.03 ) and the barrier layer (GaAs) respectively. ...
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... This is performed using a non-linear least-squares fitting procedure (Kobayasi and Nara 1993). More details about the method are reported in Gueddim et al. (2006Gueddim et al. ( , 2007Gueddim et al. ( , 2015, and Gueddim and Bouarissa (2009). ...
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... More details about the procedure for bulk semiconductors are reported in Refs. [28][29][30]. ...
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We demonstrate working prototypes of a GaInNAs-based solar cell lattice-matched to GaAs with photoresponse down to 1 eV. This device is intended for use as the third junction of future-generation ultrahigh-efficiency three- and four-junction devices. Under the AM1.5 direct spectrum with all the light higher in energy than the GaAs band gap filtered out, the prototypes have open-circuit voltages ranging from 0.35 to 0.44 V, short-circuit currents of 1.8 mA/cm2, and fill factors from 61% to 66%. The short-circuit currents are of principal concern: the internal quantum efficiencies rise only to about 0.2. We discuss the short diffusion lengths which are the reason for this low photocurrent. As a partial workaround for the poor diffusion lengths, we demonstrate a depletion-width-enhanced variation of one of the prototype devices that trades off decreased voltage for increased photocurrent, with a short-circuit current of 6.5 mA/cm2 and an open-circuit voltage of 0.29 V.
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The group III nitrides (AlN, GaN and InN) represent an important trio of semiconductors because of their direct band gaps which span the range 1.95-6.2 eV, including the whole of the visible region and extending well out into the ultraviolet (UV) range. They form a complete series of ternary alloys which, in principle, makes available any band gap within this range and the fact that they also generate efficient luminescence has been the main driving force for their recent technological development. High brightness visible light-emitting diodes (LEDs) are now commercially available, a development which has transformed the market for LED-based full colour displays and which has opened the way to many other applications, such as in traffic lights and efficient low voltage, flat panel white light sources. Continuously operating UV laser diodes have also been demonstrated in the laboratory, exciting tremendous interest for high-density optical storage systems, UV lithography and projection displays. In a remarkably short space of time, the nitrides have therefore caught up with and, in some ways, surpassed the wide band gap II-VI compounds (ZnCdSSe) as materials for short wavelength optoelectronic devices. The purpose of this paper is to review these developments and to provide essential background material in the form of the structural, electronic and optical properties of the nitrides, relevant to these applications. We have been guided by the fact that the devices so far available are based on the binary compound GaN (which is relatively well developed at the present time), together with the ternary alloys AlGaN and InGaN, containing modest amounts of Al or In. We therefore concentrate, to a considerable extent, on the properties of GaN, then introduce those of the alloys as appropriate, emphasizing their use in the formation of the heterostructures employed in devices. The nitrides crystallize preferentially in the hexagonal wurtzite structure and devices have so far been based on this material so the majority of our paper is concerned with it, however, the cubic, zinc blende form is known for all three compounds, and cubic GaN has been the subject of sufficient work to merit a brief account in its own right. There is significant interest based on possible technological advantages, such as easier doping, easier cleaving (for laser facets) and easier contacting. It also appears, at present, that the cubic form gives higher electron and hole mobilities than the hexagonal form. The dominant hexagonal structure is similar to that found in a number of II-VI compounds such as CdS and they can therefore be taken as role models. In particular, the lower symmetry gives rise to three separate valence bands at the zone centre and exciton spectra associated with each of these have been reported by many workers for GaN. Interpretation is complicated by the presence of strain in many samples due to the fact that most material consists of epitaxial thin films grown on non-lattice-matched substrates (bulk GaN crystals not being widely available). However, much progress has been made in understanding the physics of these films and we discuss the current position with regard to band gaps, effective masses, exciton binding energies, phonon energies, dielectric constants, etc. Apart from a lack of knowledge of the anticipated valence band anisotropy, it can be said that GaN is now rather well documented. Less detail is available for AlN or InN and we make no attempt to provide similar data for them. The structure of the paper is based on a historical introduction, followed by a brief account of the various crystal growth methods used to produce bulk GaN and epitaxial films of GaN and the ternary alloys. This is then followed by an account of the structural properties of hexagonal GaN as measured by x-ray diffraction and electron microscopy, phonon properties from infrared and Raman spectroscopy, electrical properties, with emphasis on n- and p-type doping, and optical properties, measured mainly by photoluminescence. A brief comparative account of cubic GaN properties follows. Discussion of alloy properties in the context of their use in quantum well and superlattice structures forms an introduction to the device sections which close the paper. These include details of the technology necessary for etching, contacting and forming laser facets, as an introduction to recent results on LEDs and laser diodes. Having described the current position, we speculate briefly on likely future developments.
Article
During the last few years the developments in the field of III-nitrides have been spectacular. High quality epitaxial layers can now be grown by MOVPE. Recently good quality epilayers have also been grown by MBE. Considerable work has been done on dislocations, strain, and critical thickness of GaN grown on different substrates. Splitting of valence band by crystal field and by spin-orbit interaction has been calculated and measured. The measured values agree with the calculated values. Effects of strain on the splitting of the valence band and on the optical properties have been studied in detail. Values of band offsets at the heterointerface between several pairs of different nitrides have been determined. Extensive work has been done on the optical and electrical properties. Near band-edge spectra have been measured over a wide range of temperatures. Free and bound exciton peaks have been resolved. Valence band structure has been determined using the PL spectra and compared with the theoretically calculated spectra. Strain and its effect on the optical properties of the III-nitride layers have been studied both theoretically and experimentally. Both n and p conductivity have been achieved. InGaN quantum wells with GaN and AlGaN barriers and cladding layers have been investigated. PL of the quantum wells is affected by confinement effects, band filling, quantum confined Stark effect, and strain. This work has led to the fabrication of advanced optoelectronic and electronic devices. The light-emitting decodes emitting in the blue and green regions of the spectrum have been commercialized. The work leading to these developments is reviewed in this article. The device processing methods and actual devices are not discussed.
Article
Self-consistent linear muffin-tin-orbital band-structure calculations are used to investigate the optical and structural properties of III-V semiconducting nitrides under hydrostatic pressure. The pressure behavior of the energy band structures is discussed in the context of the postulated chemical trends in III-V semiconductors. The regions in k space of dominant interband contributions to the elements of structure in the dielectric functions are identified. The total-energy calculations suggest that all the nitrides under pressure transform to the semiconducting rocksalt phase. The calculated transition pressures are 21.6 GPA (InN), 51.8 GPa (GaN), 16.6 GPa (AlN), and 850 GPa (BN). Experimental values that agree well with this have been found for the first three compounds. The fact that GaN and AlN have such different transition pressures in spite of their very similar ionicities is explained by the presence of 3d states on Ga.
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