摘要:

We investigated the effect of hydrogen ion shower doping on polycrystalline silicon thin‐film transistors (p‐Si TFTs). Hydrogen atoms were introduced to the channel region ofp‐Si TFTs by PH3/H2ion shower doping of the source/drain contact. Hydrogen concentration in the channel region can be controlled by altering the gate metal thickness. Hydrogen atoms affect the TFT’s threshold voltage shifts until it becomes negative, inn‐type TFTs. The threshold voltage shift depends on the hydrogen content of the channel region inp‐Si TFTs. This is explained by the existence of Si−3trap states in the grain boundaries. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114171

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have studied the formation of cuspidal pits during the growth of strained SixGe1−xalloy layers at relatively high supersaturations. The pit formation is directly linked to strain in the alloy layer, and we propose a heterogeneous formation mechanism in which the pits develop from stress‐driven surface diffusion associated with a localized initial perturbation of the buffer layer surface. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114172

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The initial stage of AlN film growth on 6H‐SiC(0001) substrates by plasma‐assisted, gas source molecular beam epitaxy (PAGSMBE) has been investigated in terms of growth mode and interface defects. Cross‐sectional high resolution transmission electron microscopy (HRTEM) was used to observe the microstructure of the deposited films and the AlN/SiC interfaces. Surface morphologies and interface atomic structures were compared between films grown on vicinal and on‐axis surfaces. Essentially atomically flat AlN surfaces were obtained using on‐axis substrates. This is indicative of two‐dimensional growth to a thickness of ∼15 A˚. Islandlike features were observed on the vicinal surface. The coalescence of these features at steps gave rise to double positioning boundaries (DPBs) as a result of the misalignment of the Si/C bilayer steps with the Al/N bilayers in the growing film. The quality of thicker AlN films is strongly influenced by the concentration of DPBs formed at the outset of growth. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114173

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

It is shown that critical thicknesses of In0.65Ga0.35As epilayers, grown by molecular beam epitaxy on lattice matched InAlAs/InP heterostructures, are affected by surface steps and excess arsenic, i.e., nonstoichiometry, in the overgrowth. The critical thickness is reduced in the presence of steps, but is observed to increase when the excess arsenic atoms are present in the layer. It is argued that the generation of dislocation loops required for misfit dislocations is facilitated at the step edges. The resulting misfit dislocations augment the strain relaxation produced by the glide of threading dislocations in the epilayers. On the other hand, the internal strains associated with the nonstoichiometry strengthens the lattice, thus making dislocation glide difficult which delays the relaxation process. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114175

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Photoluminescence spectra from the Si impurity center in diamond films grown by chemical‐vapor deposition techniques were studied at temperatures between 9 and 300 K. Laser excitation at 514.5 nm, and resonant with the zero‐phonon absorption line at 737 nm (1.6823 eV), were used. Luminescence lines become narrowed at resonance excitation, and the vibrational structure of the Si center was observed with a major phonon replica at 767 nm (1.6165 eV). The observed vibrational energy of 515 cm−1supports a diatomic quasi‐molecular Si2center structure. Temperature dependencies of the linewidth of the zero‐phonon line and its phonon replica were measured and the origins of the broadening are discussed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114176

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The hardness and elastic behavior of Fe–Ag (001) multilayered thin films is presented. Significant enhancements in the hardness were observed that followed a Hall–Petch‐type dependence on bilayer thickness. A reduction in the flexural elastic modulus of 55% relative to the large bilayer thickness value was observed when the bilayer thickness was reduced to 5 nm. Concomitant with the elastic modulus reduction was a variation in the interplanar spacing perpendicular to the plane of the film. It is shown that these behaviors are generally consistent with a model based on the effects of interface stresses. Using this model, an interface stress for Fe–Ag (001) of approximately −1.8 N/m was obtained. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114177

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Oxidized porous silicon is known to luminesce efficiently and with a ns‐fast response in the green‐blue region of the spectrum (2.3–2.7 eV) at room temperature. For microporous Si processed by rapid thermal oxidation at 1100–1200  °C in a dry oxygen ambient, we observe that the blue light has a time‐delayed component that indicates carrier trapping. In addition to the well‐established ultrafast light (∼1 ns) a signal with a time delay of order 1 s is present under UV photoexcitation. The time‐delayed blue light exists at low temperature and has an excitation onset edge at 4.3±0.1 eV, an energy that is usually associated with a band discontinuity at the Si–SiO2interface. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114178

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Segregation of column III atoms during molecular beam epitaxy of III‐III’‐V semiconductor compounds causes nonabrupt interfaces and a surface composition different from the bulk one. To derive concentration profiles, a thermodynamical equilibrium model has been used for a long time. This model applies well to describe segregation processes at high growth temperatures, but fails in predicting concentration profile variations with substrate temperature. We have thus developed a kinetic model which correctly takes into account the evolution with the growth temperature. We apply this model to the case of indium segregation in the GaxIn1−xAs/GaAs system. The calculated indium concentration profiles are compared to those obtained with the thermodynamical equilibrium model. A kinetic limitation of segregation is shown to appear at low substrate temperatures and sufficiently high growth rates. This limitation is predicted to arise below 400 °C for a growth rate of 1 monolayer/s for In segregation in the GaxIn1−xAs/GaAs system. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114180

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A systematic study of the substrate orientation effect on crystalline quality of GaAs grown by molecular beam epitaxy at low substrate temperature (215 °C) was performed using double‐crystal x‐ray diffractometer and transmission electron microscopy. The crystal quality was found to be strongly correlated with substrate orientations. Layers of high crystalline perfection with excess arsenic were obtained on both GaAs(100) and (311)B substrates, while columnar polycrystalline growth was observed on (211)B substrate. The transition from a single crystalline state to a polycrystalline state was clearly demonstrated by a 0.5 &mgr;m GaAs layer on (111)B surface. Surface kinetic factors are believed to play important roles during the low temperature growth. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114181

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In spite of much work, the formation of epitaxial CoSi2from Ti/Co on (100) Si remains something of a mystery. It has been proposed that epitaxy occurs via the formation of an intermediate phase of CoSi with a (311) preferred orientation. In the absence of sufficient information it is impossible to validate or to invalidate the specific original claim. However, one shows that the formation of preferably oriented CoSi is not a necessary condition for the subsequent growth of epitaxial CoSi2. Careful measurements of diffraction intensities reveal the probable, temporary formation of a metastable form of CoSi2, based on a diamond cubic rather than the usual CaF2structure. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114182

出版商:AIP    

年代:1995

数据来源: AIP