This is a report on the first setup of a recently developed, extremely sensitive and very fast 3D quadrupole ion trap mass spectrometer inline in a metalorganic vapour phase epitaxy (MOVPE) system. This setup was developed ultimately for the decomposition- and the interaction analysis of various established as well as novel metalorganic sources for MOVPE deposition of III/V semiconductors. To make in-situ gas phase and growth interaction analysis on a new level of sensitivity possible without disturbing the MOVPE growth process itself, an optimized experimental connection of the mass spectrometer to the MOVPE system is required. This work reports on the realization of such an experimental setup and provides first proof of concept for decomposition analysis. In addition, a comparison to previous studies and gas-phase analysis at MOVPE systems will be given in this work.

N containing lattice matched 1 eV materials, such as Ga(NAsSb) and (GaIn)(NAs), are discussed as potential solar subcells in a four junction solar cell alongside Ge, GaAs, and (GaIn)P, reaching theoretically conversion efficiencies of around 50 %. The solar subcell with the highest conversion efficiency, consisting of (GaIn)(NAsSb), was grown with molecular beam epitaxy (MBE). The growth of Sb/N containing materials have always been a challenge to metalorganic vapor phase epitaxy (MOVPE), as N incorporation is hindered drastically by even small amounts of Sb if 1,1-dimethylhydrazine is used. This strong N/Sb interaction was not observed by MBE, therefore gas phase reactions in MOVPE are held responsible for the N incorporation drop. In this work we will present a systematic study of Ga(NAsSb) on GaAs grown in MOVPE with the novel N/As precursor di-tertiary-butyl-arsano-amine, as well as triethylgallium and triethylantimony. The achieved 1 eV Ga(NAsSb) material opens up new possibilities for using MOVPE to grow further solar subcells like (GaIn)(NAsSb) or Ga(NAsSb) in the band gap range of 1.0 – 1.1 eV.

III−V semiconductors containing small amounts of nitrogen ("dilute nitrides") are very promising material systems for optoelectronic applications. Devices based on dilute nitrides currently suffer from problematic C incorporation. To overcome this problem, a novel nitrogen (N) and arsenic (As) precursor for metal−organic vapor phase epitaxy (MOVPE) of the dilute nitride di-tertbutylaminoarsane (DTBAA) has been introduced. DTBAA in comparison to the commonly used 1,1-dimethylhydrazine (UDMHy) showed a significantly improved N incorporation efficiency. The molecule exhibits no strong carbon (C)−N bond, and the C is only present in large alkyl groups which form fewer C radicals since β-H elimination is the dominating decomposition process. This should significantly lower the problematic C incorporation in dilute nitrides and lead to highly efficient devices. To understand the high N incorporation efficiency as well as the As incorporation, the gas-phase decomposition of this novel precursor has been studied with a real time Fourier transform (FT) quadrupole ion trap mass spectrometer (iTrap) from Carl Zeiss SMT GmbH in a horizontal Aixtron Aix 200 GFR MOVPE reactor. Formation of isobutane and isobutene proves a radical cleavage and β-H-elimination as decomposition processes of the tert-butyl groups attached to the molecule. Furthermore, the appearance of ammonia (NH 3 ) has been detected. This indicates a direct cleavage of the As−N bond of the molecule, resulting in the formation of an aminyl radical (NH 2• ). The formation of NH 2 • explains the high N incorporation efficiency of DTBAA as well as its limitations due to desorption of NH 3 at higher temperatures.

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