摘要:

Argon, hydrogen, and germane plasmas were investigated in a variably configured radio frequency (rf) diode glow‐discharge reactor system with a range of rf powers. Plasma parameters such as electron temperature, plasma density, plasma potential, and floating potential were determined and the internal distribution of voltages within the glow discharge was considered. An equivalent circuit for the discharge is presented and fundamental dependence between the voltage ratio and the electrode area ratio of squared power law compared with the usual fourth power law is measured and described. The main goal of this work was to obtain more information about the energy of ion bombardment on the growing film surface.

ISSN:0021-8979    

DOI:10.1063/1.350820

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Remote‐plasma‐activated chemical‐vapor deposition (RPACVD) is a method whereby thin films are deposited with the substrate located out of the plasma zone. The lower rate of energetic ion and photon bombardment in RPACVD compared to conventional direct‐plasma‐enhanced chemical‐vapor deposition (DPECVD) reduces damage to the substrate. The use of RPACVD also enables one to more carefully tailor the flux of radicals to the substrate compared to DPECVD. This selectivity results from both physically isolating the substrate from undesirable radicals and limiting the variety of chemical pathways that produce radicals. A model for RPACVD is described and results from the model are discussed in the context of comparing gas mixtures and geometries in which this selectivity may be achieved. The chemistries investigated are Rg/SiH4(Rg=Ar, He) for deposition of Si and Rg/NH3/SiH4(Rg=Ar, He) for deposition of Si3N4. It is found that the selectivity in producing radicals that can be obtained by excitation transfer from excited states of rare gases is easily compromised by reactor configurations that allow injected gases to penetrate into the plasma zone.

ISSN:0021-8979    

DOI:10.1063/1.350821

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The popular two‐moment expansion of the Boltzmann equation is developed for cases involving significant generation of electrons by ionization. In particular, this formulation enhances the determination of electron velocity distribution functions at high values ofE/Nwhere ionization becomes significant. The simple two‐moment approach allows such calculations to be made with modest computing resources. Examples are given of two such calculations in an inert gas (argon), and the numerical approach for these is outlined. Comparison with published experiments is shown to be very good, in both the low‐E/Nand high‐E/Nregimes. In one example, comparison with published results from a very general numerical procedure is found to be excellent.

ISSN:0021-8979    

DOI:10.1063/1.350822

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The Stutzmann, Jackson, and Tsai model [Phys. Rev. B32, 23 (1985)] for the creation of metastable defects in illuminateda‐Si:H by tail‐to‐tail recombination of electrons and holes and conversion of weak bonding and antibonding orbitals into dangling bonds has been extended to include the exponential nature of tail states and saturation of dangling bond density. A first‐order approximation of the general result gives a stretched exponential formula similar to that of Redfield and Bube [Appl. Phys. Lett.54, 1037 (1989)] removing an apparent contradiction between the two models. The theory is also extended to include the thermal annealing process. This gives an apparent saturation of dangling bond density at a steady state equilibrium valueNmwhich tends to the actual saturation valueNsas the intensity of illumination is increased.

ISSN:0021-8979    

DOI:10.1063/1.350823

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Deep‐level transient spectroscopy has been used to monitor the effect of carrier concentration on the properties of radiation‐induced defects in InPn+pmesa diodes grown by metalorganic chemical vapor deposition. The activation energyEafor hole emission from H4 and H5 centers and the injection‐enhanced annealing rate of H4 at 200 K have been measured as a function of carrier concentrationNAover the range ∼1×1016– 4×1017cm−3. The measured values ofEadecrease with increasingNAin a way that can be semi‐quantitatively explained by a combination of the Frenkel–Poole effect and phonon‐assisted tunneling produced by the electric field in the junction. The results suggest that hole emission from H4 and H5 centers takes place to maxima in different valence bands. The injection‐enhanced annealing rate of H4 centers increases with increasingNAat low concentrations, but approaches a maximum value nearNA∼ 1017cm−3, indicating a limiting dopant (Zn) concentration for impurity‐enhanced defect annealing.

ISSN:0021-8979    

DOI:10.1063/1.351386

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The multi‐shot evolution of laser‐induced periodic structure was studied by the time‐resolved optical diffraction and reflection from the surface of polycrystalline silicon‐on‐insulator during the accumulation of 20 ns ruby laser pulses. In contrast to the results previously reported for the bulk sample, it was observed that the channel of the periodic structure development changed during the multiple irradiations even with a fixed fluence. The observed change occurs because the energy absorption is enhanced by the presence of the periodic structure preformed by the preceding pulses, and the absorbed laser energy at the polycrystalline layer is insulated by the underlying SiO2layer. A previously unappreciated dip structure was observed in the time‐resolved diffraction and a possible explanation is suggested postulating the preferential energy deposition in the valleys of the periodic structure.

ISSN:0021-8979    

DOI:10.1063/1.350799

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Schottky barrier structures have been formed by the deposition of Cu and Pt onn‐type Si(100) at room temperature. The structures were irradiated by 300 keV protons or 1.3 MeV alpha particles to doses between 109and 1010cm−2. Deep level transient spectroscopy measurements performed in the temperature range 80–290 K revealed a new level ∼0.31 eV below the conduction band edge in the proton‐bombarded Cu/Si(100) samples. The level exhibits metastable properties, and reversible cycling of its strength can be accomplished by a procedure where thermal annealing, forward biasing (hole injection), and white light excitation are undertaken. Evidence is presented showing that the level is associated with both Cu and H. Furthermore, the production rate of electrically active defects, e.g., divacancy and vacancy oxygen centers, is found to be substantially lower in the Cu/Si(100) samples compared with Pt/Si(100) samples irradiated under identical conditions. This is attributed to passivation of the irradiation‐induced acceptor centers by fast diffusing interstitial Cu+, and in particular, the effect is more pronounced at shallow depths close to the Cu/Si interface than in the deep tail beyond the implantation peak.

ISSN:0021-8979    

DOI:10.1063/1.350800

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A systematic study of nitride‐phase formation in iron implanted with nitrogen was performed by conversion electron Mo¨ssbauer spectroscopy (CEMS). The samples of &agr;‐iron were implanted at room temperature with 100 keV N+2ions whose mean range in the iron target was about 55 nm. The implanted dose varied from 5×1016to 6×1017N atoms/cm2. After implantation each sample was isothermally annealed in vacuum for 1 h at temperatures from 150 to 500 °C in 50 °C steps. The CEMS measurements allowed identification of the iron nitride phases formed by implantation and after annealing. At low doses (up to 1.5×1017N atoms/cm2), the nitrogen‐containing &agr;’‐martensite and/or &agr;‘‐Fe16N2phases appear. For intermediate doses (2×1017–2.7×1017N atoms/cm2) &egr;‐Fe3N is formed additionally. For doses higher than 3×1017N atoms/cm2the dominant phase is &egr;‐Fe2N. In the course of annealing, &egr;‐Fe2N decomposes to &egr;‐Fe3N and &ggr;’‐Fe4N and finally disappears at about 300–350 °C. At 500 °C only the Zeeman sextet of &agr;‐Fe remains in the spectra. Considerable nitrogen release as detected by nuclear reaction analysis accompanied the phase evolution during annealing. These measurements lead to a new phase diagram for the implanted FeN system.

ISSN:0021-8979    

DOI:10.1063/1.350801

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Effects of ion implantation of 320 keV28Si at room temperature in pseudomorphic metastable GexSi1−x(x≊0.04, 0.09, 0.13) layers ∼170 nm thick grown on Si(100) wafers were characterized by x‐ray double‐crystal diffractometry and MeV4He channeling spectrometry. The damage induced by implantation produces additional compressive strain in the GexSi1−xlayers, superimposed on the intrinsic compressive strain of the heterostructures. This strain rises with the dose proportionally for doses below several times 101428Si/cm2. Furthermore, for a given dose, the strain increases with the Ge content in the layer. Upon thermal processing, the damage anneals out and the strain recovers to the value before implantation. Amorphized samples (doses of greater than 2×101528Si/cm2) regrow poorly.

ISSN:0021-8979    

DOI:10.1063/1.350802

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Compositionally graded films of SiGe/Si(100) and GaInAs/GaAs were grown under different conditions in order to investigate the different modes of strain relaxation associated with the compositional grading. We show that, when the growth conditions are very clean and the gradient is shallow enough (about 1% misfit per half micron), very good, relaxed films are obtained. This coincides with the introduction of large numbers of dislocations in the substrate itself, which is counter‐intuitive at first since the substrate is under negligible strain. We show that this introduction of dislocations is the result of the activation of novel Frank–Read‐like sources located in the graded region, and is directly correlated to the lack of other low energy nucleation sites for dislocations. We detail the conditions of growth necessary for this phenomenon to occur, and show that it operates both for the SiGe/Si system and the GaInAs/GaAs system. Pure, relaxed Ge films have been grown in this manner on Si(100), with a defect density as low as 106/cm2.

ISSN:0021-8979    

DOI:10.1063/1.350803

出版商:AIP    

年代:1992

数据来源: AIP