摘要:

(AlxGa1−x)0.51In0.49P layers, lattice matched to (001)‐oriented GaAs substrates, have been grown throughout the entire aluminum composition range fromx=0 to 1.0 by atmospheric pressure organometallic vapor‐phase epitaxy (OMVPE), using trimethylaluminum (TMAl), trimethylgallium (TMGa), trimethylindium (TMln), and phosphine (PH3) as source materials in a horizontal reactor. The growth temperature was held constant at 680 °C. Excellent surface morphologies were obtained over the entire composition range. Unlike previously reported results, neither high growth temperatures nor low pressures were needed in order to obtain good‐quality, high‐x(AlxGa1−x)0.51In0.49P alloys using trimethylalkyls. Photoluminescence (PL) was observed, even at 300 K, for all samples with Al solid compositions ofx≤0.52. The results show that the energy band gap measured by PL at room temperature for this material varies asEg=1.9 +0.6x, in accord with previous studies. It was found that the PL emission intensity was nearly constant at 10 K with increasingxin the range from 0 to 0.52. This contrasts with earlier published results which showed a decreasing PL intensity for the higher values ofx. The 300‐K PL intensity was almost a constant forx≤0.3 and gradually decreased with increasing Al content forx>0.30. The dependence is nearly that predicted from a simple calculation based on the relative occupancies of the &Ggr; andXconduction bands using a constant minority‐carrier lifetime. The PL full width at half maximum (FWHM) forx=0 was 7.2 meV at 10 K and 35 meV at 300 K. These are the narrowest reported results to date. Forx=0.48, the FWHM was 31 meV at 10 K and 78 meV at 300 K. It was observed that at both 10 and 300 K, the FWHM increased slowly with increasing aluminum concentration.

ISSN:0021-8979    

DOI:10.1063/1.346101

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Under certain conditions the process of thin‐film epitaxy can be envisioned as atom deposition onto a crystalline substrate with subsequent surface diffusion along the surface terraces and eventual atomic bonding at a surface step. This process of step‐mediated growth is currently being explored as a mechanism to form two‐dimensional periodic structures. Such schemes require a periodic step distribution, i.e., uniform terrace lengths, to succeed. In this paper we use a model based on step‐mediated growth to present an analytical derivation of the approach to uniform terrace lengths on a stepped surface, given a terrace length distribution of finite width at the outset. The results show that growth interruption is of no advantage and that in general the approach to uniform terrace lengths is quite slow. The width of the terrace length distribution varies approximately as the inverse 4th root of the deposited coverage. This will only occur if the atoms attach themselves predominately at the up‐step of each terrace. Otherwise, the width of the distribution will grow without bounds. The model further predicts characteristic oscillations of terrace lengths in the vicinity of multiple height steps.

ISSN:0021-8979    

DOI:10.1063/1.345754

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have demonstrated the feasibility of heteroepitaxial growth of Ga0.51In0.49P/GaAs layers on Si substrates by low‐pressure organometallic vapor phase deposition. The growth parameters of the GaAs buffer layer were confirmed to be the controlling factors in obtaining higher quality Ga0.51In0.49P on Si. Under the optimum growth conditions, specular single‐crystal Ga0.51In0.49P layers can be reproducibly obtained. The room‐temperature electron mobility of the undoped Ga0.51In0.49P epilayer can reach 1000 cm2/V s with a carrier concentration of 2×1016cm−3. The efficient photoluminescence indicates that the Ga0.51In0.49P grown layer is of high optical quality. In addition, the GaAs intermediate layer is also effective in reducing the residual tensile stress in the Ga0.51In0.49P film on Si. The results presented can compete with those reported previously for the OMVPE‐grown GaxIn1−xP on GaAs substrates.

ISSN:0021-8979    

DOI:10.1063/1.345755

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The effects of phosphorus, arsenic, and boron on surface‐energy‐driven secondary grain growth (SEDSGG) in thin polycrystalline silicon films have been investigated. At concentrations at or above 5×1020cm−3, phosphorus and arsenic were found to markedly enhance SEDSGG while boron had little effect. However, codoping with phosphorous and boron or arsenic and boron lead to compensation (reduction or elimination) of the enhancement effect. The kinetics of SEDSGG were analyzed using transmission electron microscopy. In order to identify electronic as well as segregation effects of dopants on the kinetics of SEDSGG, electron concentrations in the Si films were determined from Hall measurements and dopant segregation was directly measured using scanning transmission electron microscopy and energy‐dispersive x‐ray analysis. Analogous to normal grain growth, dopant‐induced enhancement of SEDSGG can be explained in terms of an increased grain‐boundary atomic mobility due to changes in point‐defect concentrations resulting from changes in the Fermi level. The effects of codoping on segregation of dopants at grain boundaries was found to have no appreciable effect on the rate of SEDSGG.

ISSN:0021-8979    

DOI:10.1063/1.345756

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

An investigation of techniques for the preparation and preservation of stoichiometric InGaAs and InP surfaces, and techniques for regenerating these surfaces in vacuum have been carried out using x‐ray photoelectron spectroscopy for surface characterization. It was found that InGaAs stoichiometric surfaces grown by molecular‐beam epitaxy (MBE) can be preserved from oxidation and contamination by condensation of a thin layer of arsenic in the MBE chamber. The stoichiometric surfaces can be regenerated by thermal desorption of the arsenic cap in vacuum. Although stoichiometric InP surfaces can be prepared and arsenic capped in the MBE chamber, interfacial alloying between the arsenic cap and the substrate occurred during the thermal desorption process. Stoichiometric InGaAs and InP surfaces can also be preserved by a UV/ozone‐formed oxide overlayer. For the removal of ozone‐formed native oxides, thermal desorption at 458 °C regenerated clean and stoichiometric InP surfaces with a band bending of less than 0.3 eV on bothn‐ andp‐type substrates. However, complete oxide desorption on InGaAs required a temperature, above 565 °C, at which the surface decomposed. It was found that the ozone‐formed surface oxides on InGaAs and InP could be removed at a substrate temperature below about 250 °C using a remote hydrogen plasma. The resultantn‐InGaAs substrate surface was close to flat band, whereas the surface Fermi levels of then‐ andp‐type InP substrates were at 0.4 and 0.7 eV from the conduction‐band minimum, respectively.

ISSN:0021-8979    

DOI:10.1063/1.345757

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The effects of addition of Si2F6to low‐pressure chemical vapor deposition of W using WF6and H2was studied. Adding sufficient Si2F6gas enhances the deposition rate (RD) of W film in the WF6and H2system by a factor of 2 over a wide range of deposition parameters, that is, the substrate temperature and the partial pressures of H2, WF6, and Si2F6. W films deposited under the conditions where the enhancement ofRDoccurs have a resistivity as low as that of films deposited in the WF6and H2system, except for some W films exhibiting &bgr;‐W structure, and have no Si contamination. The origin of the enhancement ofRDby adding Si2F6is discussed.

ISSN:0021-8979    

DOI:10.1063/1.345730

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The diffusion of thin, highlyp‐doped layers in AlGaAs/GaAs single‐ and double‐heterostructures, grown by metalorganic vapor‐phase epitaxy, was studied withC‐Vetch profiling and secondary ion mass spectroscopy. The effect of different post‐growth heat treatments was investigated and diffusion coefficients for both magnesium and zinc were measured. It was found that Mg diffuses about twice as fast Zn and that the order of magnitude of the diffusion coefficient is 10−14cm2 s−1at 900 °C, the exact value being process and concentration dependent. A model based on the interstitial–substitutional diffusion mechanism with suitable kinetic limitations was successfully used to simulate the observed dopant concentration profiles.We also found an anomalous strong diffusion of zinc from GaAs into highlyn‐doped AlGaAs. Detailed results on this and other structures are presented and implications for optimal design of heterostructure devices such as bipolar transistors are discussed.

ISSN:0021-8979    

DOI:10.1063/1.345731

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The lattice mismatch in and out of the orientation direction was measured in layers of CoSi2grown by high dose implantation and annealing. A comparison of (111), (100), and (110) orientations showed that the lateral mismatches were similar but the perpendicular mismatch increased monotonically through the series. The differences in the degree of relaxation of the three orientations provide a possible explanation for the observed anisotropy in the electrical properties.

ISSN:0021-8979    

DOI:10.1063/1.345732

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Molecular‐beam epitaxial growth of GexSi1−xon ⟨100⟩ porous Si substrate was studied using Rutherford backscattering spectrometry, transmission electron microscopy, and defect etching. This study was stimulated by the theoretically predicted possibility of stress field reduction in a lattice‐mismatched film grown on a patterned substrate. The experimental results show predominantly 60° dislocations with long misfit segments, and no reduction of dislocation density is observed by the use of porous Si substrates. The nature of interconnected growth area of the porous Si substrate is believed to be the reason for the ineffectiveness of the stress reduction.

ISSN:0021-8979    

DOI:10.1063/1.345733

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A new Al(111)/Si(111) orientational epitaxy using x‐ray pole figure analysis is reported. The new structure has a 19° rotation with respect to the parallel epitaxy. The results are explained using a geometrical lattice matching concept.

ISSN:0021-8979    

DOI:10.1063/1.345734

出版商:AIP    

年代:1990

数据来源: AIP