M. Druminski

Unexpectedly high energy photoluminescence of highly Si doped GaAs grown by MOVPE

Abstract Epitaxial GaAs films highly doped with silicon were grown by the MOVPE method in the TMGa-AsH 3 -SiH 4 -H 2 system. The films were investigated by Hall measurements, photoluminescence (PL) studies and SIMS. A linear relationship between the silane mole fraction in the gas phase and the incorporated Si in the epitaxial films was established by SIMS measurements. The Si concentrations of the samples investigated range from 3×10 18 to 1×10 20 atoms/cm 3 , whereas the corresponding Hall concentrations are in the range from 2×10 18 to 5.5×10 18 cm -3 . They show a linear increase for the lower Si concentrations and then turn to a decrease for higher Si concentrations. The Hall mobilities decrease with increasing Si mole fraction (2320 to 760 cm 2 /V · s, 300 K). The intensities of the near band gap PL are markedly higher and the emission is shifted to higher energies by up to 60 meV as compared to melt- or solution-grown n-GaAs of the same concentration range. It appears that among the different growth techniques the MOVPE process gives highly doped n-type GaAs:Si samples which are more close to perfection.

SELECTIVE ETCHING AND EPITAXIAL REFILLING OF SILICON WELLS IN THE SYSTEM SiH4/HCl/H2

Wells were etched in (100) silicon by different kinds of selective etching and were selectively refilled by using different gas systems. Masking materials were SiO2 and Si3N4; for the refilling the systems SiCl4/H2 and SiH4/HCl/H2 were studied. By using a combination of weak anisotropic gas etching with HCl (Si3N4 films as mask) and of SiH4/HCl/H2 as refilling system, plane surfaces without ridges at the boundary of the mask and without nuclei on the mask were reached. The results were obtained by SEM, light microscopic and profile investigations and are compared with the other kinds of etching and refilling.

Planar selective area growth of DH laser structures using hydrides, tertiarybutyl and ditertiarybutyl group V precursors in MOMBE

In Metal Organic Molecular Beam Epitaxy (MOMBE) the selective area epitaxy (SAE) of double heterostructures (DH) lasers was investigated by using as group V starting materials tertiarybutylarsine/tertiarybutylphosphine (TBAs/TBP), ditertiarybutylarsine/ditertiarybutylphosphine (DTBAs/DTBP) and AsH 3 /PH 3 . In Zn-doped InP layers a reduced doping efficiency was found for the process using organic group V precursors whose dissociation chemistry can explain this observation. The growth of GaInAsP close to InP (Q 1.05) using TBAs/TBP reveals that there is a distinct change in the elemental incorporation compared to the hydride process. Thus individual tuning of the growth parameters for different precursors is required. The selectively grown laser ridge structures compare well with large-area grown reference structures. The shape of the ridge is perfectly rectangular when Be-doped p-type cladding layers are used, whereas Zn doping yields a slight multifacet formation at the ridge sidewalls.

The combination of two growth methods for the epitaxial deposition of silicon films on insulating substrates

Abstract Thin epitaxial silicon films (0.5–3 μm) on spinel and sapphire are produced by using a combination of two growth methods. After complete coverage of the substrate surface with silicon by decomposition of silane with a high deposition rate (e.g. 2–3 μm/min), hydrogen chloride is added to the gas stream without changing the silane amount. By the first step reactions between silicon and the substrate surface are reduced to a minimum. During the second step the net growth rate decreases to ≈0.3 μm/min. Silicon layers grown by this process are more homogeneous and perfect than films of equal thickness grown with a constant rate. The better quality is connected with lower optical absorption coefficients and increase in silicon surface smoothness. The silicon growth rate as a function of the hydrogen chloride flow is in good agreement with theoretical and experimental results already published in literature.

Very low threshold current density (Al)GaInAs/Al(Ga)InAs laser structures grown by atmospheric pressure MOVPE

The growth of (Al)GaInAs/Al(Ga)InAs structures of high quality for laser devices using metalorganic vapor-phase epitaxy (MOVPE) at atmospheric pressure is described. SeH/sub 2/ and DEZn have been used as the dopant precursors. Se is an appropriate dopant for the n-type confinement layers of lasers, showing a distinctly higher electrical activation in AlInAs than Si. Zn is superior to Mg as a dopant for the p-type confinement layers of lasers as its apparent diffusion coefficient is about one order of magnitude lower than that of Mg in AlInAs. Broad-area double-heterostructure (DH) lasers (device length=800 mu m) operating at 1.66 mu m and 1.55 mu m are shown to have I/sub th/ values as low as 2.3 kA cm/sup 2/ and 1.5 kA/cm/sup 2/, respectively. With broad-area separate-confinement-heterostructure multiple-quantum-well (SCH-MQW) lasers (device length=800 mu m) emitting at 1.524 mu m, threshold current densities as low is 0.92 kA/cm/sup 2/ can be achieved.<<ETX>>