The structure of compressively strained (GaIn)(NAs)/GaAs multi-quantum wells (MQWs) grown by MOVPE is investigated using TEM. The quaternary, metastable material exhibits a high structural perfection if a N concentration of 4% is not exceeded. Phase separation or clustering effects are not observed, and the In is dispersed homogeneously throughout the quantum wells. The interface roughness of the quantum wells to the GaAs barriers is in the order of several monolayers. Increasing the N content to above 4.5% results in a deterioration of the structure and of the homogeneity of the wells

We report on recent results obtained using an AIX 2400G3HT production type Planetary Reactor® in the 5×3 inch configuration for growth of typical group-III nitride layer structures consisting of GaN, InGaN and AlGaN. The optimum reactor geometry has been found by extensive modeling of the reactor design. Increased thermal management allows maximum reactor temperatures above 1400°C. As a consequence of extensive reactor modeling, the process transfer from 6×2 inch to 5×3 inch configuration was carried out by simple scaling of the corresponding process parameters of the 6×2 inch configuration. The scaling factor is calculated with respect to the changed reactor geometry. We used optical reflectrometry for in-situ growth control during this process development and could confirm the theoretical scaling requirements for obtaining identical growth conditions as compared to the 6×2 inch reactor configuration. This is verified by the generation of identical reflectance spectrum features. This important issue of in-situ control is discussed in detail. The TMGa efficiency could be kept at about 17%. Switching to the 8×3 inch configuration the efficiency increases up to about 27%, which is an improvement of 63% as compared to the 6×2 inch configuration

The surface chemical states of MOCVD grown GaN, AlGaN and InGaN, and the influence of different dopants have been studied with x-ray photoelectron spectroscopy (XPS). The results show that for most of the samples the N 1s peak can be fitted with a dominant GaN peak at the binding energy of 397.2 ± 0.2 eV and a small N-H peak at the binding energy of 398.5 ± 0.2 eV, while Ga 3d can be deconvoluted into three peaks, i.e., elemental Ga at 18.5 ± 0.1 eV, GaN at 19.7 ± 0.1 eV, and Ga2O3 at 20.4 ± 0.1 eV. Si-doping appears to have small influence on the surface chemical states of GaN. Compared with Si-doping, the influence of Mg-doping appears -to be larger. In addition to a change in the component intensities, Mg-doping also causes the N ls and Ga 3d peaks to broaden. The ternary AlxGa1−xN (x ∼ 0.025) sample shows aluminum surface segregation, while the undoped InxGa1−xN(x ∼0.12) shows indium surface deficiency

Recent advances in the preparation of gallium nitride (GaN) and related compounds have made possible the production of blue semiconductor laser. Conventional preparation involves growing GaN thin films on lattice-mismatching sapphire using metal-organic chemical vapor deposition (MOCVD). In this article, we describe an alternative method to produce a lattice-matching strained layer in GaAs for subsequent GaN growth by plasma immersion ion implantation (PIII) followed by rapid thermal annealing. Our novel approach uses broad ion impact energy distribution and multiple implant voltages to form a spread-out nitrogen depth profile and an amorphous surface layer. This approach circumvents the retained dose and low nitrogen content problems associated with ion beam implantation at fix energy. Based on our Raman study, the resulting structure after PIII and rapid thermal annealing is strained and contains some GaN possibly in crystal form

The nitrogen containing alloy GaInNAs has attracted a great deal of interest recently for optoelectronic device applications at long wavelengths, especially 1.3µm, on GaAs substrates. What has been observed is that the material quality degrades rapidly with the addition of nitrogen. In this work we systematically explore the parameter space for the growth of GainNAs using plasma-assisted MBE and inert gas dilution. Inert gas dilution allows additional control of the production of active nitrogen; thus we can independently adjust RF power, gas flow rate, and nitrogen generation, which is used to study the effects of the plasma on the growth surface. In addition to examining the effects of plasma operating conditions, we will also explore the effects of other growth parameters (arsenic to nitrogen ratio and growth temperature) on the resultant structural and optical properties. These properties will be explored by photoluminescence, SIMS, and x-ray diffraction with the goal of understanding how nitrogen incorporation affects the resultant material properties. The resulting information is used to grow high quality layers for GaNAs avalanche photodiodes with a cut-off wavelength of 1.064µm

Using micro-Raman scattering we have studied atomic distribution and the ordering effects in GaN-rich GaNP layers on (0001) sapphire substrates grown by electron cyclotron resonance molecular beam epitaxy (ECR-MBE). Raman spectrum from layers grown at higher temperatures (≥700°C) shows coexistence of GaP-rich region with cubic symmetry and GaN-rich region with hexagonal symmetry. Sharp TO and LO phonon lines, indicative of {111} ordering in the GaP region are observed. Increasing phosphorous (P >1.5%) in GaNP alloy leads to phase separation that is reflected in the suppression of GaN-like Raman modes. The phase-separated region shows an additional Raman line at 384 cm−1 between the TO and LO phonon of GaP due to strongly confined LO phonon in ordered {111} (GaP)n(GaN)m nanometer size clusters. Decreasing growth temperature increases the phosphorous concentration in the GaNP layer and disorder activated acoustic modes appear in the Raman spectrum as a result of symmetry break down. When phosphorous concentration reaches 8.2 % in the layer grown at 570°C, Raman spectrum shows broad amorphous like bands indicative of short-range ordering