Reaction of E t,A s with AsCl, in n-pentane yields dimeric [Et,A sX AsC13]2 in quantitative yield; sublimation in vacuo affords white crystals. X-Ray diffraction data were collected at 133 K (3149 independent observed reflections; R = 0.029. Rw = 0.026). Crystal data: monoclinic space group P2,/c, a = 761.9(8). b = 1118.8(4). c = 1406.0(14) pm; ß = 100.90(4)°. Z = 2 dimers. The dimer contains a planar A s2Cl6-unit with terminal and bridging As —Cl bonds; each arsenic atom is bonded to a Et3As molecule via an arsenic—arsenic bond. The dimer thus has pseudo fourand six-coordinate arsenic atoms.

We present a two-step growth process for ZnO on GaN templates to achieve high-quality ZnO layers with XRD rocking curve FWHMs of the (0002) reflection of ∼180″ and narrow cathodoluminescence of 1.3meV of the dominant I8 emission. These layers are applied for an investigation of potential nitrogen doping sources to achieve p-type doping of ZnO, namely NH3, UDMHy, and NO. Of these sources NO seems to induce only little changes in the optical and electrical properties of the material. A brownish colour of the samples is observed when using NH3 or UDMHy at higher dopant flows. With it we find an increase in the electron carrier concentration from 1016cm−3 to above 1018cm−3. For some samples grown with lower dopant flows, we observe a decrease in the carrier concentration upon annealing to values significantly lower than the background doping concentration when using UDMHy. The sample which shows the strongest decrease in the carrier concentration also shows a pronounced DAP emission which vanishes upon annealing, most likely due to activation of an acceptor state.

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.

High-quality ZnO was grown by metal organic vapor phase epitaxy on 1.3 µm thick GaN layers on Si(111) using dimethylzinc and tertiary-butanol as precursors. The variation of the growth temperature shows a strong correlation with the microstructure as observed by atomic force and scanning electron microscopy. With increasing growth temperature we find an increasing size of ZnO crystallites and a transition from 3D to 2D growth. Moreover, increasing the growth temperature leads to a reduction of tensile stress in the ZnO as observed by X-ray diffraction. In highly spatially resolved cathodoluminescence measurements we observe narrow (A0,X) luminescence from the ZnO surface and a strong donator correlated luminescence at macroscopic defects.

Metal organic chemical vapor phase epitaxy-grown ZnO layers using iso-propanol and DMZn as oxygen and zinc precursors, respectively, are presented. The layers were grown on GaN templates in the temperature range 400-475 degreesC at a reactor pressure of 300-500 mbar with VI/Il ratios around 45. A columnar structure with an average column size of 6.5 mum in diameter and a roughness of 70 nm (r.m.s.) is observed by atomic force microscopy measurements. In X-ray diffractometry reciprocal space maps the ZnO peak splits up indicating differently strained layers. An approximately 100 nm wide distorted transition region between the GaN and ZnO layers is found in these measurements. The low-temperature cathodoluminescence spectra are dominated by narrow nearband-edge emission and almost no deep defect-related luminescence is found. A pronounced spectral blue shift is found in the growth direction, which is attributed to the relaxation of the tensile stress and associated with inner fields. A strong microscopic correlation between the surface morphology and the emission of the acceptor bound excitons is observed.

ZnO is a promising material for light emitters in the UV region. For MOCVD growth no well-suited O-precursor is available. Three different high-purity oxygen precursors, i.e. iso-propanol, acetone, and N2O were tested for the growth of ZnO on GaN/Si(111) templates. For iso-propanol pre-reactions are observed influencing the growth rate and limiting the growth temperature to below 500°C. Best layer quality is obtained around 450°C at 300mbar reactor pressure and a VI–II ratio larger than 40. ZnO grown in a similar growth regime but using acetone as O-precursor exhibits a surface constructed from nanometer sized filaments. Most of the acetone-grown films have growth orientations of (101̄1). Using N2O higher growth temperatures are needed due to the poor decomposition of this gas. However, no prereactions are observed and (0002) oriented layers with good X-ray ω-scans at ZnO-positions can be obtained around 800°C at 300mbar and a VI–II ratio above 600.

The C- and O-incorporation behaviour in (AlGa)As (0⩽x⩽1) epitaxial layers grown by metal organic vapour phase epitaxy (MOVPE) using tertiary butyl arsine (TBAs) has been investigated in detail by means of calibrated SIMS, XRD, and Hall studies. A variety of both trimethyl gallium (TMGa), trimethyl aluminum (TMAl) as well as TBAs batches has been used to grow (AlGa)As epitaxial layers in the temperature range of 625–725°C using different V/III-ratios (2.5 up to 40) and reactor pressures were in the range of 50–200mbar. The primary source of C is the methyl group of the group-III-compounds. The C-level shows a quadratic reduction as a function of the V/III-ratio for ratios up to 10 and a smaller decline for high V/III-ratio. O-contamination in the (AlGa)As layers originates both from some batches of TMAl as well as TBAs. Two O-sources are identified in some TBAs batches due to their characteristic O-incorporation behaviour, which significantly deviates from that reported for AsH3-growth. Using specific purification steps of the TBAs these impurities were drastically reduced. State of the art low O-content (AlGa)As with O-levels of 1×1018cm−3 for an Al-concentration of 85% and 2.5×1016cm−3 for 30% (AlGa)As are achieved at low growth temperatures of 625°C. The realization of low-O-content, high-quality (AlGa)As at low substrate temperature and almost independent of the used V/III-ratio in the MOVPE using TBAs offers new possiblities in the application of highly strained materials or critical doping layer profiles in advanced device structures, which at present are not accessible by using AsH3.

Thermal decomposition studies and low pressure metalorganic vapour phase epitaxy (MOVPE) growth experiments have been performed using novel, less toxic arsinetrialkyl sources, which decompose by the β-hydride elimination process. Therefore, As–H functions are automatically formed in the hot temperature zone of the MOVPE reactor to enable high quality layer deposition. Decomposition studies have been carried out under growth conditions in the MOVPE reactor by quadrupole mass spectroscopy (QMS). The β-elimination decomposition of the novel As-sources diethyltertiarybutyl-arsine (DE t BAs) and diethylisopropyl-arsine (DE i PrAs) is proven by the detection of the cracking products diethylarsine (DEAsH) and the corresponding alkene fragments isobutene ( C4H8) and propene ( C3H6), respectively. The alkene-to-radical formation for different As- and P-precursors indicate a β-elimination efficiency of about 60% for tertiarybutyl- and 40% for isopropyl-groups, whereas for ethyl groups no significant indication of a β-elimination has been observed. GaAs bulk layers were grown by using trimethylgallium (TMGa) in combination with the β-eliminating As-trialkyl sources DE t BAs and DE i PrAs, respectively, as well as by using TEAs or DEAsH, both decomposing under ethyl-radical formation. In addition, the partially fluorinated source pentafluorethyl-diisopropyl-arsine (PFED i PrAs) has been investigated, however, only an etching of the GaAs substrate surface could be detected independently of the growth conditions. The use of β-eliminating As-trialkyl compounds leads to significantly improved layer properties as compared to TEAs-grown structures. GaAs layers, grown with DE t BAs or DE i PrAs at substrate temperatures of 600–650° C and V/III ratios between 8 and 80 exhibit p-type behaviour with net carrier concentrations of 3–5×1015 cm-3 and hole mobilities of 350–400 cm2/ V·s at 300 K and 3500–4100 cm2/ V·s at 77 K. Carbon is the dominant acceptor impurity in GaAs layers at present, as determined by PL spectroscopy. These results indicate a promising potential of the class of β-eliminating As-compounds as replacements for arsine in the MOVPE.

Metalorganic vapour-phase epitaxy (MOVPE) growth experiments for GaAs and (AlGa)As have been performed as a function of growth temperature and VIII ratio using the new alternative precursor diethyl-tert-butylarsin (DEtBAs) in combination with trimethylgallium (TMGa) and trimethylaluminium (TMAl). The incorporation of deep traps has been investigated by means of photoluminescence (PL) and deep level transient Fourier spectroscopy (DLTFS). In (AlGa)As layers grown with DEtBAs a drastic reduction of the deep broad band luminescence between 1.5 and 2 eV is observed in dependence of the growth conditions. A probably deep complex defect involving an As vacancy is observed in (AlGa)As layers grown with DEtBAs. In GaAs layers grown with DEtBAs or AsH3 the dominant deep trap is the EL2 defect. Deep level photoluminescence studies show a reduced incorporation of the EL2 defect as compared to AsH3 grown layers, due to the smaller VIII ratio. The obtained low deep defect concentration in particular for GaAs layers underlines the great potential of the model precursor DEtBAs as substitute for the highly toxic AsH3 in MOVPE.

The novel β-hydride eliminating trialkyl-As compounds diethyl-tertiarybutyl-As (DEtBAs) and diethyl-isopropyl-As (DEiPrAs) has been used as less toxic substitutes for AsH3 for both thecleaning of oxide passivated GaAs wafers prior to growth and the subsequent metalorganic vapour phase epitaxy (MOVPE), layer deposition of GaAs, AlAs and (AlGa)As. High-resolution X-ray diffraction and scanning electron microscopy have been used to investigate the structural properties of GaAs/AlAs superlattices that were grown directly onto differently pretreated GaAs wafer surfaces without buffer using different As precursors in combination with TMGa, TEGa and TMAl. Nucleation problems due to the formation of a contamination layer onto the wafer surface after the pretreatment as well as binary growth rates and incorporation efficiencies of Al and Ga into (AlGa)As have been studied. An optimized preparation sequence with respect to annealing times and temperatures using the trialkyl-As sources is presented. This pretreatment procedure ensures ideal nucleation of the GaAs/AlAs superlattice structures. For the use of the novel β-eliminating As compounds instead of AsH3, no changes of the growth rate dependence for the binary GaAs and AlAs layers and an identical incorporation behaviour in ternary (AlGa)As have been observed in the mass transport limited growth regime.

The key feature of the novel trialkyl-group-V-precursors is the insitu formation of group-V-H-functions in the hot temperature zone of the MOVPE reactor by the R-elimination process, as verified by decomposition studies of diethyltertiarybutyl-arsine (DEtBAs) under MOVPE growth conditions. The results for the optimization of the MOVPE growth of GaAs using several batches of different compounds in combination with standard TMGa as determined by use of the temperature-dependent Hall- and photoluminescence (PL) technique are presented and discussed. Reproducible residual p-type-doping levels of 3-5*10(15) cm(-3) with hole mobilities of up to 390 cm(2)/Vsec at 300 K are observed, Mg being the dominant acceptor impurity at present as determined by PL spectroscopy. Deep level photoluminescence studies show a reduction of the deep defect EL2 as compared to AsH3-grown layers, due to the smaller V/III ratio.

In this study we report on the chemical synthesis, thermal decomposition and first metal-organic vapour-phase epitaxy (MOVPE) growth studies for a new class of metal-organic As compounds, designed as substitutes for the highly toxic AsH3. The key feature of these molecules is the in-situ formation of AsH functions only in the hot temperature zone of thw MOVPE reactor. Compounds with the principal molecular structure As(Rrad)n(Rβ)3−n(n=0, 1, 2; Rrad≡ alkyl group with radical formation, Rβ ≡ alkyl group with β elimination) do not a priori contain the AsH bonds needed for the growth of high quality III–V semiconductors using MOVPE; they are formed in situ in the reactor by thermal decomposition. The postulated β elimination process has been proven by decomposition studies using an ersatz reactor system with quadrupole mass spectrometry for the potential β elimination groups isobutyl and tert-butyl. The principal methods of synthesis of high purity arsenic compounds are presented and discussed. In addition we describe experiments for the MOVPE of GaAs epitaxial layers with the model compound diethyl-tert-butylarsine (DETBAs). The residual impurity levels of GaAs epitaxial layers grown in combination with trimethylgallium for different batches of DETBAs are presented and discussed as a function of the MOVPE growth conditions.

We report on the chemical synthesis, thermal decomposition studies and the first low pressure MOVPE growth experiments for a new class of metalorganic As compounds, designed as substitutes for the highly toxic AsH3. The key feature of these molecules is the in-situ formation of As-H-functions, formed by thermal decomposition under β-elimination only in the hot temperature zone of the MOVPE reactor. As a model precursor, the As-source diethyl-tertiarybutyl-arsine (DETBAs) has been synthesized. The expected thermal decomposition mechanism of this molecule under β-elimination, studied in an ersatz reactor system at low pressure, is proved by the detection of the products diethylarsine (DEAsH) and the stable isobutene (C4H8) in the mass spectra as cracking pattern. In first LP-MOVPE growth experiments, DETBAs has been used in combination with the standard group (III) sources TMGa and TMAl to realize GaAs and (AlGa)As bulk layers as well as AlAs/GaAs superlattices. The influence of growth parameters on the structural and electrical quality of the epilayers is presented and discussed by means of high-resolution X-ray diffraction, interference microscopy and Hall investigations. Smooth surface morphologies and narrow X-ray diffraction linewidths are achieved for GaAs (12“ FWHM) and (AlGa)As (13“ FWHM), as well as for AlAs/GaAs superlattices (SL main peak: 11.5“ FWHM; SL sattelite peak: 15.3“ FWHM). All layers exhibit n-type carrier concentrations, caused by residual impurities in the used batches of DETBAs. Best results show impurity levels of ND − NA = 3 × 1016 cm-3 with electron mobilities of μ = 4800 cm2/V·s at 77 K. These first results render this class of molecules as very interesting and promising substitutes for the group V hydrides.