C. Vèrié

Growth of AlSb on insulating substrates by metal organics chemical vapour deposition

Abstract Aluminium antimonide thin films were grown on different insulating substrates, i.e. silica, CaF 2 , BaF 2 , Al 2 O 3 , GaAs, by metal organics chemical vapour deposition (MO-CVD). Epitaxial AlSb thin films were successfully grown on CaF 2 and GaAs. In the process, the metal alkyls trimethylaluminium (TMA) and trimethylantimony (TMSb) are the sources of Al and Sb, respectively. The thermodynamic study of the system Al-Sb-C-H shows that AlSb could be deposited for given values of the partial pressures of Al, Sb and C in the vapour phase. Other condensed phases could appear, Al 4 C 3 , Sb.

Heteroepitaxy of GaAs on Si: The effect of in situ thermal annealing under AsH3

This letter shows that an in situ thermal annealing step in AsH3/H2 during the metalorganic vapor phase epitaxy of GaAs on Si(001) improves the crystalline quality. The dislocation density is reduced (below 107 cm−2) without affecting the Si diffusion across the heterointerface or the strain level in the epilayer. The nature of the various near‐band‐gap recombinations present in the unannealed and annealed samples is discussed in light of selective photoluminescence experiments.

Evidence by Raman spectroscopy and x‐ray diffraction of a strong influence of H2O traces on the metalorganic vapor phase epitaxy of GaAs on Si

The metalorganic vapor phase epitaxy of GaAs on Si is shown to be strongly sensitive to the residual water vapor content in the growth reactor atmosphere. This finding is evidenced both by Raman spectroscopy and double‐crystal x‐ray diffraction. For the growth of good crystalline quality GaAs on Si, the upper hygrometric level limit is found around 0.5 ppm by volume.

High efficiency conversion of laser energy and its application to optical power transmission

The authors address several aspects of the optical power transmission concept: the modeling of monochromatic conversion efficiency versus matched bandgap of a photovoltaic (PV) cell, parameterized as a function of illumination intensity; the selection criteria of the suitable semiconductors which are expected to have the highest PV conversion efficiency for the various applications; laboratory experimental study using an (Al,Ga)As laser beam transmitted through an optical fiber: a GaAs-based PV cell, designed for being set up at the optical fiber extremity, has been grown by MOVPE and has demonstrated an efficiency of 52.8% under 14-W/cm/sup 2/ illumination. Several future applications, concerning transmission of optical power in space and from space, or through optical fiber in terrestrial utilizations, are discussed.<<ETX>>

INFLUENCE OF MOVPE GROWTH-PARAMETERS ON THE STRUCTURAL AND OPTICAL-PROPERTIES OF GAAS ON SI(100)

Abstract The influence of various parameters such as the initial low temperature buffer layer and layer thickness on the overall MOVPE-grown GaAs on Si crystal properties has been investigated. An accurate control of the initial buffer layer, nucleating as a three-dimensional island on Si (TEM results), induces a substantial defect reduction in GaAs on Si epilayers. Further defect reduction is achieved by in-situ high temperature annealing (850°C) under AsH 3 /H 2 flow during growth. No change of the silicon cross diffusion profile (SIMS) or residual stress magnitude was observed, in contrast with post-growth annealing processes which are shown also to affect detrimentally the optical properties. Moreover, the modification of the main residual acceptor species and the (100) coplanar tensile stress in GaAs on Si is discussed in the light of photoluminescence spectroscopy.

High pressure dependence of the electronic properties of bound states in n-type GaAs

Abstract High pressure dependence of photoluminescence spectra in n-type doped GaAs, performed at liquid helium temperature, is shown to give some new insight into the electronic structure of bound states in this III–V compound and related alloys. In addition to some expected features, the evidence of several new pressure-induced effects leads to the discussion of some important electronic properties e.g., departure from the Γ1c minimum proximity for donor levels occuring prior to the Γ-X cross-over, metal-to-nonmetal transition. An unexpected finding in the present study is a clear observation of nitrogen-related intense lines, suggesting a possible systematic N-doping of molecular beam epitaxy-grown GaAs:Si.

Minority‐carrier lifetime study of the pressure induced Γ‐X crossover in GaAs

Room‐temperature continuous and time‐resolved (on a nanosecond scale) photoluminescence experiments have been performed on p‐type GaAs. Observation of indirect luminescence in GaAs above 4 GPa allowed a direct determination of the room‐temperature pressure coefficient of the Xc1 valleys. A new set of pressure dependence parameters for both Γ and X energy gaps in GaAs has been determined. These pressure coefficients, together with the intensity of luminescence as a function of pressure, yielded an estimate of the electron lifetime ratio confirmed by subsequent time‐resolved experiments. A threefold enhancement of electron lifetime is observed above the Γ‐X crossover.

Epitaxial growth of InAs1−xSbx alloys by MOCVD

InAs1−xSbx is one of the most promising alloys for achieving high performance III–V photodetectors. MOVPE of this solid solution from TEI, TMSb and AsH3 was successful both on (0001) Al2O3 and (111) InAs substrates (with respectively x < 0.1 and x ⩽ 0.23) from 520 to 580°C. Intermediate layers permit accomodation of the lattice mismatch between the substrate and the ternary alloy.

Beryllium substitution-mediated covalency engineering of II–VI alloys for lattice elastic rigidity reinforcement

This work is focused on the classical IIB-VI wide-band-gap compound-based device problem, e.g. the elusive longevity of [(Zn,Cd)-VI]-based blue lasers. Starting with new data, it follows our first proposals (1994, 1995) of novel Be-chalcogenide potentialities. Its foundation is the identification of a structural signature of the epitaxial layer lattice. i.e.. the shear modulus C 8 = (C 11 - C 12 )/2, together with its improved calculation versus a Harrison covalency parameter deduced from his LCAO model. This work confirms the possibility of achieving an elastic rigidity reinforcement of the lattice in (Zn,Cd)-Vl alloys through alloying with Be, paving the way to what we call a covalency engineering in the II-VIs. We have discovered the existence of Be-based alloys that are Si lattice-matched, a novel application of silicon which was mentioned in our previous proposals.

Metalorganic chemical vapor deposition of YBa2Cu3O7-x using a special equipment for solid precursors

Abstract YBaCuO thin films here grown by chemical vapour deposition using Y(dpm) 3 , Ba(dpm) 2 and Cu(acac) 2 as metal precursors. A specific design of the solid precursor processing system was developed to achieve run-to-run reproducibility. A superconducting transition was observed with T c onset = 94 K and T c ( R = 0) = 92 K for as-grown layers cooled in O 2 for YBA 2 Cu 3 O 7- x films deposited on {100}SrTiO 3 substrates.