Doped Si Atoms Research Articles

Photovoltaic In 0.5Ga 0.5As/GaAs quantum dot infrared photodetector with a single-sided Al 0.3Ga 0.7As layer

We investigated a photovoltaic three-stacked In 0.5Ga 0.5As/GaAs quantum dot infrared detector (QDIP) with an Al 0.3Ga 0.7As single-sided blocking layer. We observed broad photocurrent spectra in the photon energy range of 120–400 meV ( λ ∼ 3–10 μm) at zero-bias voltage, due to the photovoltaic effect at low temperatures. The peak responsivity was about 10.5 mA/W at a photon energy of 200 meV ( λ ∼ 6.2 μm) at T = 40 K. The large photovoltaic effect in our detector was a result of the enhanced asymmetric band structure, caused not only by the segregation of highly doped Si atoms, but also by the single-sided Al 0.3Ga 0.7As layer beneath the top contact layer.

InAs/GaP/InGaP high-temperature power Schottky rectifier

An InAs/GaP/InGaP rectifier has been fabricated using a semiconductor-semiconductor “Schottky” junction to utilize the thermal stability of the semiconductor-semiconductor interface. The InAs/GaP/InGaP system demonstrates rectifying characteristics with an ideality factor of 2.3 and a current–voltage extracted barrier height of 0.96 eV. It exhibits low reverse bias leakage current and achieves breakdown electric field of 0.6 MV/cm. The InAs/GaP/InGaP system maintains the rectifying characteristics up to 600 °C. Further improvement of the thermal stability is expected to be achieved by reducing the diffusion of Si dopant atoms across the InAs/GaP interface at high temperature.

Mechanisms for Si dopant migration in molecular beam epitaxy AlxGa1−xAs

Because of well-known surface segregation effects in molecular beam epitaxy growth, Si dopant atoms deposited as thin layers in AlxGa1−xAs typically become distributed over many atomic layers. We have measured the Si depth distributions in (100) and (311)A samples grown at temperatures between 420 and 655 °C, with Al fraction x=0, 0.1, and 0.32. The surface migration decay length Λ for a Si atom on a growing (100) surface is strongly temperature dependent but nearly independent of x, with Λ≈8 nm at 655 °C. The x=0(100) measurements show evidence for a minimum value Λ≈0.6 nm at low temperatures and a maximum value Λ≈8.5 nm at high temperatures. The data are in accord with a thermally activated surface segregation process with activation energy (1.8±0.4) eV acting in parallel with a temperature independent surface segregation mechanism. The (311)A surface shows Λ=(3.3±0.1) nm virtually independent of temperature for x=0. The Si decay length for the (311)A surface strongly increases with x, and for x=0.32 there is no significant difference in Λ for the (100) and (311)A surfaces.

Investigation of deep levels in rapid thermally annealed SiO2-capped n-GaAs grown by metal-organic chemical vapor deposition

Defects created in rapid thermally annealed (RTA) SiO2-capped epitaxial GaAs layers grown by metal-organic chemical vapor deposition have been investigated by deep level transient spectroscopy. RTA introduced four electron traps S1 (Ec−0.23 eV), S2 (Ec−0.46 eV), S3 (Ec−0.72 eV), and S4 (Ec−0.74 eV). S1 may be the so-called EL9 defect. We propose that S2 is a defect complex involving the Ga vacancy and Si dopant atoms, VGa–SiGa, and associate it with the EL5. S2 is introduced almost uniformly within the first 0.8 μm below the surface with an activation energy of 4.4 eV. S4 is most probably one of the EL2 family. The concentration of S4 decreased exponentially below the surface with a characteristic decay length ∼0.2 μm. The activation energy for the introduction of S4 is 2.5 eV.

Diminution of Carrier Concentrations in S + ‐ Implanted GaAs during Cooling from a High Annealing Temperature

The surface of sulfur (S)‐implanted gallium arsenide (GaAs) was covered with hydrogenated amorphous silicon (a‐Si:H) film and subsequently heated to 1000°C. Silicon amounts larger than the implanted dose of ions diffuse from the a‐Si:H film into GaAs during annealing. The GaAs had sheet carrier concentrations smaller than that of doped Si atoms. The carrier concentrations decreased with increasing time on cooling from the annealing temperature of 1000 to 50°C, whereas the S and Si atom concentrations were independent of the cooling time. © 2000 The Electrochemical Society. All rights reserved.

Charge screening around Si dopant atoms in GaAs by X-STM

In this contribution we show that the screening effect around the Si dopant atoms in GaAs can be observed not only at low temperature, as reported earlier, but also at room temperature.

Raman scattering studies on Si-doped GaAs grown by hydrogen-assisted molecular beam epitaxy

The surfactant effect of atomic hydrogen on the incorporation of silicon into (100)-, (111)A-, and (311)A-oriented GaAs grown by hydrogen-assisted molecular beam epitaxy has been studied with Raman spectroscopy. Local vibrational modes (LVMs) of SiGa and SiAs impurities are observed for excitation nearly resonant with the E1 energy gap. Site switch of the doping Si atoms from Ga to As lattice sites due to the surfactant effect of H during growth of the high-index doped layers was directly monitored by changes of the normalized intensity of the LVMs. An increase of the free carrier concentration in p-type samples and a decrease in n-type samples resulting from this site switch were also observed in the plasmon-phonon coupled modes as observed in Raman scattering. Similar changes in carrier concentrations were observed by means of electrical transport measurements.

Raman scattering investigation on the ordered incorporation of Si dopant atoms on GaAs(001) vicinal surfaces during MBE growth

Using Raman scattering by local vibrational modes (LVM) and collective electronic excitations we have investigated the ordered incorporation of Si dopant atoms on vicinal GaAs(001) surfaces. LVM spectra revealed for a sequence of δ-doped samples grown by molecular beam epitaxy (MBE) under specific conditions that the Si dopant atoms are predominantly incorporated on Ga-sites even at a doping concentration as high as 1.8 × 10 13 cm −2. For a sample grown under conditions established by real-time high-energy electron diffraction (RHEED) to be favourable for the wire-like Si incorporation, a pronounced polarization asymmetry in the Raman scattering intensity of collective intersubband plasmon-phonon modes arising from the δ-doping layer has been found.

Substrate photoluminescence: An aid in the evaluation of pulsed laser evaporation and epitaxial growth of Cd1−xMnxTe epilayers on (111)GaAs

Photoluminescence (PL) emitted from (111)Cd1−xMnxTe/(111)GaAs:Si heterojunctions produced using pulsed laser evaporation and epitaxy (PLEE) has been studied at 11.5 K. The heterojunctions show PL from the substrate E0 and E0+Δ0 gap regions as well as from the epilayer. The substrate E0+Δ0 signal is particularly sensitive to the epilayer growth temperature and is strongest for samples grown on substrates held at Tg=290 °C. The heterojunction PL also includes a component produced by Si dopant atoms in the substrate that undergo clustering changes as the growth temperature is raised. Through comparison with annealing studies of the substrate, it is argued that the PLEE ablated material possesses sufficient kinetic energy to increase the effective temperature above Tg at the growth surface.

Raman spectroscopic study on the wirelike incorporation of Si dopant atoms on GaAs(001) vicinal surfaces

Raman scattering by collective electronic excitations from a δ-doping layer has been used to investigate the ordered incorporation of Si dopant atoms on vicinal GaAs(001) surfaces. In a series of δ-doped samples grown by molecular beam epitaxy (MBE) under specific conditions the Si dopant atoms were found to be incorporated predominantly on Ga sites, even at a doping concentration as high as 1.8×1013 cm−2. A pronounced polarization asymmetry in the Raman scattering intensity of collective intersubband plasmon-phonon modes was observed in a sample grown under conditions established by real-time high-energy electron diffraction to be favorable for wirelike Si incorporation.

Magnetotransport and magneto-optical properties of δ-doped InSb

Results of Shubnikov–de Haas (SdH), cyclotron resonance (CR), and Hall-effect measurements on δ-doped InSb:Si films grown by molecular-beam epitaxy on insulating InP substrates are reported. The investigation covers samples with sheet densities of Si dopant atoms ranging from 1×1011 to 1×1013 cm−2, temperatures from 4.2 to 300 K, and fields from 0 to 7 T. The SdH oscillations show that the samples contain electrons of two-dimensional nature, occupying multiple subbands. The effective masses obtained from the CR data correspond well to the subband occupation densities. The Hall measurements as well as the CR experiments also give evidence for the presence of additional electrons, with the conduction-band-edge mass m*=0.014m0 of bulk InSb, which exist presumably in the bulk of the films.

Deep Electron Traps In Mbe Gaas On Si

ABSTRACTDeep electron traps were investigated in MBE GaAs grown directly on Si substrates with orientations a few degrees off the <100> axis. Capacitance Deep Level Transient Spectroscopy (CDLTS) revealed the presence of eleven electron traps in the GaAs epilayer. Their activation energies ranged from 0.21 eV to 0.83 eV below the conduction band. Most of these traps were previously observed in homoepitaxial GaAs films grown under As-rich conditions (VPE, MBE), or in electron irradiated bulk GaAs. Trap concentrations tracked Si dopant density and MBE growth conditions. Observed deep levels are not introduced by metals or other contaminants present at the GaAs-Si interfaces. Rather, they are caused by defect complexes. These complexes involve native point defects, whose formation is favoured by As-rich environments, by lattice mismatch, and by different thermal expansion coefficients. Si dopant atoms may also participate in the formation of these defects. A similar deep level generation mechanism is proposed for the electron traps in homoepitaxial MBE GaAs layers.