GaP Decomposition Source Research Articles

A New Approach for Heavy N-Doping Process in Ge Epilayers Using Specific Solid Source

As an indirect band gap material, Germanium (Ge) has low efficiency of radiative recombination in the wavelength area of about 1550 nm. However, the difference between the direct and indirect band gap is very small (～140 meV) and photoluminescence emission ability of Ge could be greatly enhanced by heavy n-doping process. In this work, Ge growth directly on Si (001) substrate by molecular beam epitaxial (MBE) technique and a high n-doping level in Ge was obtained owning to using GaP decomposition source. The GaP solid source produces P2 molecules instead of P4 molecules, which have higher sticking coefficient than that of P4 comparing to the traditional doping method from PH3 gas precursor molecules. The dependence of optical property on Ge film thickness is also studied. The out-diffusion phenomenon of phosphorus dopant has been observed through SIMS profile analysis. An activated phosphorus concentration can be achieved up to more than 2 × 1019 atoms?cm&minus3 confirmed by Hall effect measurement. This result contributes to realization of Ge-on-Si devices for optoelectronic applications.

Molecular-beam epitaxial growth of tensile-strained and n-doped Ge/Si(001) films using a GaP decomposition source

We have combined numerous characterization techniques to investigate the growth of tensile-strained and n-doped Ge films on Si(001) substrates by means of solid-source molecular-beam epitaxy. The Ge growth was carried out using a two-step growth method: a low-temperature growth to produce strain relaxed and smooth buffer layers, followed by a high-temperature growth to get high crystalline quality Ge layers. It is shown that the Ge/Si Stranski–Krastanov growth mode can be completely suppressed when the growth is performed at substrate temperatures ranging between 260°C and 300°C. X-ray diffraction measurements indicate that the Ge films grown at temperatures of 700–770°C are tensile-strained with typical values lying in the range of 0.22–0.24%. Cyclic annealing allows further increase in the tensile strain up to 0.30%, which represents the highest value ever reported in the Ge/Si system. n-Doping of Ge was carried out using a GaP decomposition source. It is shown that heavy n-doping levels are obtained at low substrate temperatures (210–250°C). For a GaP source temperature of 725°C and a substrate temperature of 210°C, a phosphorus concentration of about 1019cm−3 can be obtained. Photoluminescence measurements reveal an intensity enhancement of about 16 times of the direct band gap emission and display a redshift of 25meV that can be attributed to band gap narrowing due to a high n-doping level. Finally, we discuss about growth strategies allowing optimizing the Ge growth/doping process for optoelectronic applications.

Effect of different P/As ratio on the optical and structural properties of GaAs1−xPx/GaAs

AbstractThe GaAs1−xPx/GaAs ternary alloys were grown on n‐GaAs (100) substrate with different P/As flux ratio by solid source molecular beam epitaxy (MBE) system using GaP decomposition source. In order to obtain smooth interface and lattice mismatch structures we have used both continuous growth (CG) and graded growth (GG) methods. The range of lattice parameters in the graded epilayer and phosphorous composition in the samples were determined by the high‐resolution X‐ray diffraction (HRXRD) rocking curve simulation. The critical energy points of the interband transition edges of the structures were determined by line‐shape analyses on their dielectric functions (DF) using spectroscopic ellipsometry (SE) measurements at a room temperature in the 0.5–5 eV photon energy region. Also, surface and interface phenomenon of the structures were discussed by using ellipsometric data. Phosphorous compositions of the ternary alloys were also calculated by photoluminescence (PL) emission peak positions at room temperature and using the bowing parameter obtained by fitting to critical points. Copyright © 2010 John Wiley & Sons, Ltd.

Determination of the surface segregation ratio of P in Si(1 0 0) during solid-source molecular beam epitaxial growth

The surface segregation ratio as a function of growth temperature of a dopant is a fundamental property that must be known for that dopant to be used in device applications. Using low energy secondary ion mass spectrometry, a precise determination of the segregation ratio of P in Si(1 0 0) in the temperature interval from 380 °C to 650 °C has been made. The values of the surface segregation ratios determined are substantially less than previously reported. It has been observed that the source of the P dopant as well as the temperature during growth influences the segregation of P. Using a GaP decomposition source, the deposited P has been shown to be fully electrically active in the whole growth temperature interval by measurement of the carrier concentration profiles using spreading resistance profiling.

InGaP/GaAs heterojunction bipolar transistor grown by solid-source molecular beam epitaxy with a GaP decomposition source

Lattice-matched InGaP epilayers on GaAs (001) and InGaP/GaAs heterojunction bipolar transistors (HBTs) were successfully grown by solid-source molecular beam epitaxy (SSMBE) with a GaP decomposition source. A 3 μm thick InGaP epilayer shows that low temperature photoluminescence (PL) peak energy is as large as 1.998 eV, full width at half maximum (FWHM) is 5.26 meV, which is the smallest ever reported, and X-ray diffraction (XRD) rocking curve linewidth is as narrow as that of GaAs substrate. The electron mobilities at room temperature of nominally undoped InGaP layers obtained by Hall measurements are comparable to similar InGaP epilayer grown by solid-source molecular beam epitaxy (SSMBE) with other sources or other growth techniques. The large area InGaP/GaAs HBTs show very good Dc characteristics.

Incorporation Behaviour of Arsenic and Phosphorus inGaAsP/GaAs Grown by Solid Source Molecular Beam Epitaxy with a GaPDecomposition Source

The incorporation behaviour of arsenic and phosphorus in the GaAsPternary alloy under phosphorus-rich conditions is studied based on theincorporation coefficient model and the growth diffusion model combinedwith the alloy composition data obtained by high resolution x-raydiffraction analysis. It is found that As adatoms have longer surfacelifetime and longer migration length than those of P adatoms, whichleads to an arsenic incorporation efficiency much higher than that ofphosphorous. With the increase of arsenic flux, the surface lifetime ofarsenic adatoms decreases due to the competition of As adatoms. Thedetailed analysis and discussion are given here.

Optical properties of highly disordered InGaP by solid-source molecular beam epitaxy with a GaP decomposition source

Photoluminescence (PL) spectra and Raman spectra have been utilized to study the optical properties of epitaxial InGaP grown on (0 0 1) GaAs substrate by solid-source molecular beam epitaxy with a GaP decomposition source .The 15 K PL spectrum of 3 μm-thick InGaP epilayer grown under optimized conditions ( T s=460°C, V/III=15) shows that the PL peak energy is as high as 1.998 ev and the PL full-width at half-maximum is 5.26 meV, which is the narrowest value reported. The temperature dependence of PL spectrum exhibits normal behavior. The Raman scattering spectrum at room temperature shows the ratio b/ a, where b and a represent the valley depth between the GaP- and InP-like LO peak and the InP-like LO peak height, respectively, is as high as 0.45, which is near the largest value ever reported. All these results demonstrate that the InGaP grown under optimized conditions ( T s=460°C, V/III=15) by solid-source molecular beam epitaxy with a GaP decomposition source is highly disordered.

Properties of InGaP/GaAs Grown by Solid-Source Molecular BeamEpitaxy with a GaP Decomposition Source

Lattice-matched InGaP on GaAs (001) was successfully grown bysolid-source molecular beam epitaxy with a GaP decomposition source. A0.5-µm-thick InGaP epilayer shows photoluminescence peak energy aslarge as 1.991 eV at 15 K, the full width at half maximum as small as 9.4 meVand x-ray diffraction rocking curve linewidth as narrow as 25 arcsec.The electron mobilities of undoped and Si-doped InGaP layers obtainedby Hall measurements are comparable to similar InGaP/GaAsheterojunction grown by solid-source molecular beam epitaxy with othersources or other growth techniques. The results reveal that theInGaP/GaAs heterojunction grown by the present growth way have greatpotential applications for semiconductor devices.

Growth of highly disordered InGaP on (100) GaAs by molecular beam epitaxy with a GaP decomposition source

High-quality, lattice-matched InGaP on exact (100) GaAs was successfully grown by molecular beam epitaxy with a GaP decomposition source. The ordering parameter (η) of the InGaP is investigated as a function of the growth temperature. η is as low as 0.22 and almost insensitive to the growth temperature below 460 °C. It increases abruptly around 475 °C and has a maximum value of 0.35 at ≈490 °C. Double crystal X-ray diffraction and a low-temperature photoluminescence spectrum reveal that the present growth method is robust and provides better quality InGaP compared to other state-of-the-art growth technologies.

Optical and structural properties of GaInAs/InP single quantum wells grown by solid-source MBE with a GaP decomposition source

Lattice-matched GaInAs/InP single quantum wells grown by solid-source molecular beam epitaxy using phosphorus evaporation from GaP were investigated by high resolution X-ray diffraction, low-temperature photoluminescence and time-resolved photoluminescence spectroscopy. The samples show high structural and optical quality exemplified by interference oscillations in the X-ray rocking curve, a quantum well exciton line width of 8.5 meV and a carrier lifetime of 1.3 ns.

Heavy phosphorus doping in molecular beam epitaxial grown silicon with a GaP decomposition source

Doping with phosphorus in solid source silicon molecular beam epitaxy is possible using a GaP decomposition source. This source evaporates solid GaP and is combined with an efficient mass separator system. Homogeneous P doping up to concentrations higher than 1019 cm−3 was realized. Surface accumulation of phosphorus was not observed for the low growth temperature of 400 °C used in this study. The parasitic Ga incorporation is about three orders of magnitudes below the P concentration. This new phosphorus doping technique is suitable for n-type doping in the range of 1017–1020 cm−3.

Heavy Phosphorus Doping in Molecular Beam Epitaxial Grown Silicon and Silicon/Germanium with a Gap Decomposition Source

ABSTRACTDonor-doping in silicon molecular beam epitaxy (MBE) is still an open problem, due to the low solid solubility and the strong segregation behavior (Sb, As) or to the high vapor pressure of the doping elements (P, As). Based on its high solubility elemental P2 would be the best candidate for heavy n-type doping. A new developed phosphorus source, based on the decomposition of solid GaP with a simultaneously mass separation of the parasitic Ga atoms has been applied. Homogenous P-doping higher than 1019 cm3 in Si and strained SiGe has been achieved. No surface accumulation of phosphorus was observed. The parasitic Ga incorporation is about three orders of magnitude below the P concentration. In this paper we will demonstrate the use of such cell to incorporate electrical active phosphorus during MBE growth. The incorporation probabilities into Si and strained SiGe will be compared. The dependence of segregation-/diffusion processes of phosphorus on growth temperature during the MBE will be shown. SIMS investigations on undoped Si layers reveal no P or Ga “memory effect” of the UHV equipment.

Electronic properties of InGaP grown by solid-source molecular-beam epitaxy with a GaP decomposition source

We have grown high-quality In0.48Ga0.52P layers on GaAs(001) substrates using solid-source molecular-beam epitaxy. A dimer phosphorous (P2) molecular beam was produced from a GaP decomposition source. The full width at half-maximum of the (004) double-crystal x-ray diffraction peak from a 1.7-μm-thick InGaP layer on GaAs(001) substrate was 16 arcsec, which is comparable with the smallest values ever reported. The photoluminescence linewidth at 10 K is 16 meV. Hall measurements are carried out on undoped, Si-doped, and Be-doped InGaP layers grown with a 2×1 surface reconstruction. The electron mobilities are comparable to similar InGaP/GaAs layers grown by gas-source molecular-beam epitaxy. Undoped InGaP layers grown with a 2×2 reconstruction, however, showed a high resistivity of ≥102 Ω cm at 300 K.

A GaP decomposition source for producing a dimer phosphorus molecular beam free of gallium and tetramer phosphorus

The complications arising in the molecular beam epitaxial growth of phosphides are reduced through the use of a diatomic phosphorus beam. We have fabricated a simple low-cost source for producing such a beam, suitable for a research environment.