E. Sterzer

An experimental approach for real time mass spectrometric CVD gas phase investigations

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.

Structural and electronic properties of isovalent boron atoms in GaAs

Boron containing GaAs, which is grown by metal organic vapour phase epitaxy, is studied at the atomic level by cross-sectional scanning tunneling microscopy (X-STM) and spectroscopy (STS). In topographic X-STM images, three classes of B related features are identified, which are attributed to individual B atoms on substitutional Ga sites down to the second layer below the natural {110} cleavage planes. The X-STM contrast of B atoms below the surface reflects primarily the structural modification of the GaAs matrix by the small B atoms. However, B atoms in the cleavage plane have in contrast to conventional isovalent impurities, such as Al and In, a strong influence on the local electronic structure similar to donors or acceptors. STS measurements show that B in the GaAs {110} surfaces gives rise to a localized state short below the conduction band (CB) edge while in bulk GaAs, the B impurity state is resonant with the CB. The analysis of BxGa1–xAs/GaAs quantum wells reveals a good crystal quality and show...

1 eV Ga(NAsSb) grown by MOVPE using di-tertiary-butyl-arsano-amine (DTBAA)

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.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...