In this work, we investigate the structural properties of (GaIn)(AsN)/GaAs multiple quantum wells (MQW) grown at low temperature by metalorganic vapour phase epitaxy. The structural properties, in particular the In- and N-incorporation, the lattice strain (strain modulation), the structural perfection of the metastable (GaIn)(AsN) material system and the structural quality of the (GaIn)(AsN)/GaAs interfaces are investigated by means of high-resolution x-ray diffraction, transmission electron microscopy (TEM), and secondary ion mass spectrometry. We demonstrate that (GaIn)(AsN) layers of high structural quality can be fabricated up to lattice mismatches of 4%. Our experiments reveal that N and In atoms are localized in the quaternary material and no evidences of In-segregation or N-interdiffusion could be found. TEM analyses reveal a low defect density in the highly strained layers, but no clustering or interface undulation could be detected. High-resolution TEM images show that (GaIn)(AsN)/GaAs interfaces are slightly rougher than GaAs/(GaIn)(AsN) ones.

(GaIn)(NAs)/GaAs multi-quantum-well heterostructures are grown by metal organic vapor phase epitaxy at low temperatures and are subsequently annealed in the reactor to optimize optoelectronic properties. Detailed optical and structural studies of the properties of the material, which change upon annealing under different As-stabilization as well as at different temperatures, reveal that there are two major effects of the anneal. The first one is the blue-shift of the fundamental band gap of the material, which can be attributed to a local change in the group-III environment of the nitrogen atoms. The second observation is a strong increase in photoluminescence (PL) intensity and decrease in PL linewidth upon anneal in H2-ambient, which can be attributed to the removal of non-radiative defects in the material. Chain-like N-ordering in growth direction, which induces strong inhomogeneous strain fields in the material and which can be dissolved upon anneal in H2-ambient might also act as one of the main non-radiative recombination centers in the (GaIn)(NAs) material system.

Multi-quantum well heterostructures (MQWHs) in the novel dilute nitride Ga(NAsP)/GaP material system have been grown pseudomorphically strained on GaP-substrate by metal organic vapour phase epitaxy (MOVPE). The group V-incorporation has been clarified as a function of growth temperature, chemical composition, gas phase V/V-ratios and macroscopic strain. An overall complex incorporation behaviour of the group V-atoms is observed. The precise adjustment of the V/V competition processes on the crystal surface allows, however, for a control of the solid composition of the Ga(NAsP)/GaP material system.

Compressively strained Ga(NAsP) multi-quantum-well heterostructures with As concentration above 85% have been grown pseudomorphically on GaP substrates by metal organic vapor phase epitaxy. Detailed structural analysis applying high-resolution x-ray diffraction proves the high crystalline perfection of the samples. Optical spectroscopy appyling photoluminescence and excitation spectroscopy verify the direct-band-gap characteristic of this novel material system. The comparison of the experimental data with elemental calculations via the band anticrossing model demonstrates that the formation of direct band structure can be understood by the strong bowing of the band gap energy typical for diluted III-V nitrides.

Quantum well heterostructures (QWH) in the novel dilute nitride Ga(NAsP)/GaP-material system have been grown pseudomorphically strained to GaP-substrate by metal organic vapour phase epitaxy (MOVPE). The high crystalline perfection has been determined by detailed structural analysis applying high-resolution X-ray diffrcation (XRD). The active QWH have been embedded in (AlGa)P/GaP-waveguide structures. Electrical injection lasing has been verified for broad area laser devices at low temperatures (80K - 150K) for the first time in this novel material system. (c) 2006 WILEY-VCH Veriag GmbH & Co. KGaA, Weinheim.

We investigated a GaAs0.915N0.085 single crystal under hydrostatic pressures LIP to 20 GPa by Raman spectroscopy. The zinc blende optical phonons show great similarities to those of binary GaAs under the same conditions demonstrating that nitrogen incorporation has no major influence on the GaAs-I to GaAs-II phase transition and its partial reversibility upon decompression. Frequency shifts of the nitrogen local vibrational mode under hydrostatic pressure are very different from those in binary GaN because of the different compressibilities of the two materials and the overstretched character of the Ga-N bond in Ga(As,N). This is also reflected by the anharmonicity of the Ga-N bond potential in Ga(As,N).

Realizing monolithic optoelectronic integrated circuits (OIECs) on silicon substrate would open up an exciting and completely new field of applications, i.e. optical interconnects at the chip level. In the past a lot of effort has been devoted to the growth of standard direct band gap III-V compound semiconductors on Si substrate, i.e. GaAs/Si or InP/Si. Due to the large lattice mismatch of these materials to the Si substrate large densities of threading dislocations are formed in the layers, preventing any long-term stable lasing operation of corresponding device structures. In this study the authors present a novel direct band gap material ( Ga(NAsP) ), which can be grown lattice-matched to GaP. Due to the similar lattice constant of GaP and Si, this novel material system might lead to the real monolithic integration of III/V-based optoelectronics and Si-based microelectronics in the near future

A theory is suggested for the description of luminescence in semiconductor structures, with the essential role of localized states caused by disorder. The theory is based on the set of rate equations. In contrast to most previous theoretical studies, electrons and holes are treated not in the form of excitons but rather as independent species. Theoretical results are compared with new experimental data for the time-resolved photoluminescenec in GalnNAs/GaAS quantum wells.

Highly compressively strained (GaIn)(NP) quantum wells have been grown on (1 0 0) GaP substrates by metal organic vapour-phase epitaxy (MOVPE). We achieve a high structural quality of the grown multiple quantum well structures for this novel, metastable material system. Competition between the group-V elements on the surface determines the N incorporation in Ga(NP) as well as (GaIn)(NP). For the ternary material system Ga(NP) the N content of the deposited layers does not depend on the growth rate in contrast to the quaternary system (GaIn)(NP), where the N incorporation is enhanced with increasing growth rate. This suggests a desorption controlled N incorporation process for the In-containing material. This is in accordance with the strong dependence of the N content in the material from the growth temperature and the In content. In addition — due to the metastability of the material systems under investigation — the maximal achievable N content in Ga(NP) and (GaIn)(NP) is limited when good crystal quality is to be retained.

Focus of the paper is the MOVPE process development for Al‐containing antimonides on GaSb substrates, which has been proven to be specifically challenging. First, the deoxidation of GaSb substrates was investigated. It was found that Ga2O3 is reduced to volatile Ga2O at moderate temperatures by molecular hydrogen used as carrier gas in the MOVPE environment. For the deposition of the Al‐containing antimonides DMEAA (dimethylethylamine alane) was used as Al‐precursor. Unfortunately this precursor suffers from severe pre‐reactions with other metalorganics (MO) and a low vapor pressure. To meet the challenging demands of the industrial growth of Al‐containing antimonides an AlX2600‐G3 Planetary Reactor® with new 9×2‐inch substrate configuration was developed. This is the first multiwafer reactor that was specifically designed for the growth of antimonides. Major advantages of this reactor are the reduction of pre‐reactions, higher MO efficiency as well as excellent layer homogeneity and reproducibility.

(AlInGa)P red laser diodes have become increasingly attractive as light sources for various applications. High-quality AlInGaP and InGaP layers are of key importance for the performance of these lasers. In this report we explore the metalorganic vapor phase epitaxy (MOVPE) growth of red lasers using liquid precursors, i.e. replacing the highly toxic gaseous hydrides with liquid MO-V sources. This report will show material data (X-ray, PL, SIMS, etc.) on In(Al)GaP layers grown using TBP. The material performance of AlInGaP and InGaP layers grown using TBP and having different compositions will be compared to similar layers grown using PH3. Growth parameters (temperature, V/III ratio) that will be presented will outline the advantages of MO-V growth such as lower growth temperatures and lower V/III ratios, as well as potential benefits on the maintenance of the reactor. Finally, we will show preliminary data on the full red laser epitaxial stack using the optimized growth conditions for each layer.

The effect of hydrogenation on five GaNxAs1-x epitaxial layers (0.00043less than or equal toxless than or equal to0.019) grown by metal-organic vapor-phase epitaxy was investigated. Photomodulated reflectance (PR) and photoluminescence spectroscopy were used to study the electronic band structure, and x-ray diffraction (XRD) and Raman spectroscopy to probe, respectively, the static and dynamic properties of crystal lattice before and after hydrogenation. Hydrogen almost completely neutralizes the effect of N on the band structure of the GaAs host. The direct band gap E- and the spin-orbit split-off band E- +Delta(0) blueshift toward the corresponding energies in GaAs and the E+ band disappears after hydrogenation. The PR spectra of hydrogenated GaNxAs1-x resemble broad GaAs-like spectra. The XRD traces reveal that hydrogenation removes the tensile strain in GaNxAs1-x layers and even induces compressive strain. After hydrogenation the GaAs-like features in the Raman spectra persist whereas the local vibrational mode due to N disappears. Three H-related modes can be distinguished in the Raman spectra.

An overview is presented of experimental and theoretical work oil band structure aspects of (Ga,In)(N,As) and Ga(N,As) quantum well Structures and epitaxial layers grown by molecular beam epitaxy (MBE) and metal-organic vapour phase epitaxy (MOVPE). The evolution Of unusual band structure and phonon features in GaNxAs1-x with increasing x caused by the impurity character of nitrogen in GaAs is discussed. Hydrogenation of Ga(N,As) allows one to virtually switch off the N-induced changes of the band structure and the vibrational modes. A strong blue shift up to about 100 meV of the bandgap of quaternary samples is observed on thermal annealing. The magnitude of the blue shift depends strongly on In and N concentrations as well as on the growth and annealing conditions. Raman spectra of MOVPE-grown (Ga,hi)(N,As) epitaxial layers reveal local In-N and Ga-N modes. On annealing, the intensity ratios of the local modes change, indicating a rearrangement of the nitrogen nearest-neighbour environments from Ga-rich to In-rich environments. Tight binding calculations Suggest that this might contribute strongly to the observed blue shift. Other possible contributions to the blue shift are also discussed.

We have investigated the optical properties of edge-emitting laser structures containing three Ga0.7In0.3N0.005As0.995 quantum wells embedded in GaNxAs1-x barriers grown by metal-organic vapour-phase epitaxy. In a series of three samples the nitrogen content x of the barrier was varied from 0% to 3%. We studied the optical transitions using pressure-dependent photomodulated reflectance (PR) up to 20 kbar at room temperature. Additionally we measured the pressure dependence of the lasing energy and the threshold current of the corresponding laser structures as function of hydrostatic pressure. Due to the large redshift of the Ga(N,As) band gap with increasing N of about 150 meV per percent N, the variation of x leads to a considerable change of the carrier confinement particularly of electrons. The strong increase of the threshold current of the laser device with pressure suggests a swiftly increasing threshold carrier density due to the increasing effective mass and non-parabolicity. Comparing the pressure dependence of the lasing energy and the conduction band edge supports this conclusion.

Dramatic changes of the electronic band structure occur when incorporating even a small fraction of N into GaAs. One important consequence of the N-incorporation is a strong non-parabolicity of the conduction band of GaNxAs1−x yielding already for x less than 1% a considerable increase in the electron effective mass and a strong variation of the electron effective mass with increasing k-vector. We demonstrate how this N-induced non-parabolic dispersion of the conduction band in Ga(N,As) can be determined by a careful analysis of the interband transitions of Ga(N,As)-based quantum wells as a function of hydrostatic pressure. A series of GaN0.018As0.982/GaAs wells of various widths was studied by photomodulated reflectance (PR) at 300 K and hydrostatic pressures up to 20 kbar. The PR spectra were fitted using derivative-like line shapes to extract the energy positions of the interband transitions. The transition energies were compared with theoretical values calculated using a 10-band k.p-model including the effects of nitrogen. The good agreement between experiment and theory allows one to extract the valence band offset as well as the conduction band dispersion and hence the change of the effective mass with pressure and energy.

In this study the electrical properties of the novel, metastable GaAs based material system (GaIn)(NAs) are examined. Lattice-matched (GaIn)(NAs) bulk films are grown on GaAs substrates by metal organic vapour phase epitaxy. The doping behaviour of Si, Te, Zn and Mg is examined. The background carrier concentrations in the metastable material are reasonably low, in the order of 1015/cm3 Controlled n- and p-type doping has been observed, in particular for Te and Mg, respectively, where electron and hole concentrations above 1019/cm3 can be achieved with high mobility values of up to 2000 cm2/V s for electrons and 200 cm2/V s for holes for low carrier concentrations.

The ultrafast emission dynamics of a 1.3-mum (GaIn)(NAs)/GaAs vertical-cavity surface-emitting laser is studied by femtosecond luminescence upconversion. We obtain a minimum peak delay of 15.5 ps and a minimum pulse width of 10.5 ps. Laser operation with picosecond emission dynamics is demonstrated over a temperature range from 30 to 388 K. The bandgap shift with temperature of (GaIn)(NAs)/GaAs is determined to be about - 2.9 . 10(-4) eV/K, which is smaller than for GaAs. Our measurements of the optical gain provide gain spectra similar to those of commercial (GaIn)(PAs)/InP - structures at moderate densities but broaden considerably for elevated carrier densities due to the stronger carrier confinement. We compare our experimental results with gain spectra calculated from a microscopic model and confirm the predictive capability of the model. The theoretical gain spectra are used as the input for a calculation of the temperature dependence of the (GaIn)(NAs)/GaAs surface-emitter emission which results in very good agreement with experiment.

The unusual N-induced band formation and band structure of Ga(N, As) and (Ga, In)(N, As) alloys are also reflected in the electronic structure of quantum wells (QWS) and device structures containing these non-amalgamation-type alloys. This review is divided into three parts. The first part deals with band structure aspects of bulk Ga(N, As) and motivates the possibility of a k · p-like parameterization of the band structure in terms of the level repulsion model between the conduction band edge of the host and a localized N-level. The second part presents experimental studies of interband transitions in Ga(N, As)/GaAs and (Ga, In)(N, As)/GaAs QW structures addressing band offsets, electron effective mass changes and an intrinsic mechanism contributing to the blueshift of the (Ga, In)(N, As) band gap on annealing. The observed interband transitions can be well described using a ten-band k · p model based on the level repulsion scheme. The third part deals with (Ga, In)(N, As)-based laser devices. The electronic structure of the active region of vertical-cavity surface-emitting laser and edge-emitter laser structures is studied by modulation spectroscopy. The gain of such structures is measured by optical methods and analysed in terms of a model combining the ten-band k · p description of the band structure and generalized Bloch equations.

A series of GaNxAs1-x/GaAs quantum well structures with well widths of about 20 nm and x varying between 1% and 3.5% has been grown by metal-organic vapour phase epitaxy. We have studied the evolution of the quantum well states under hydrostatic pressure up to 20 kbar at 300 K by photomodulated reflectance (PR) spectroscopy. The energy positions of the quantum well transitions have been obtained by fitting the PR spectra. The pressure dependence of the allowed heavy-hole transitions enhhn decreases with increasing n. This directly reflects the strong non-parabolic dispersion of the conduction band originating from the interaction of the N-impurity level with the bands of the GaAs host. The fitted energy positions and their pressure dependence can be well described by a 10 band k.p model. The observed splitting between the lowest light-hole and heavy-hole transitions are in agreement with a type I band alignment.

Optical gain spectra of (GaIn)(NAs)/GaAs quantum-well lasers operating in the 1.3-μm-emission-wavelength regime are measured and compared to those of a commercial (GaIn)(AsP)/InP structure. Good agreement of the experimental results with computed spectra of a microscopic many-body theory is obtained. Due to the contributions of a second confined subband, a spectrally broad gain region is expected for (GaIn)(NAs)/GaAs at elevated carrier densities.