摘要:

From considerations of dopability, band offset, and lattice match, we find that of the various heterojunctions containing II–VI compounds, then‐AlSb/p‐ZnTe heterojunction has the most promising properties for fabricating visible light emitters. The materials lattice match to 0.5%. Experimental evidence and theoretical predictions for the band offset blocking minority carrier injection indicate a range from zero to 0.3 eV maximum. This range of values is the lowest for heterojunctions involvingwide‐gapII–VI’s. Substantial electron injection into thep‐ZnTe should be possible. Control of doping may suffice to suppress undesired hole current originating in the ZnTe.

ISSN:0734-211X    

DOI:10.1116/1.584221

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

The failure of the common‐anion rule for heterojunction interfaces involving binary semiconductors has been demonstrated by many recent experiments. Wei and Zunger have explained this puzzling result in terms of a substantial role of the cationdstates in determining the valence‐band edge position. The same approach predicts that the valence‐band edge position of certain ternary semiconductors and of their quaternary alloys depends weakly on the composition. We present synchrotron‐radiation photoemission tests of these predictions.

ISSN:0734-211X    

DOI:10.1116/1.584222

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

X‐ray diffraction and photoluminescence measurements were made on InxAl1−xAs layers grown by molecular‐beam epitaxy whose lattice constants are matched, in tension, or in compression, relative to their (100)‐oriented InP substrates. Using a linear interpolation between the InAs and AlAs elastic stiffness coefficients, hydrostatic pressure coefficients, and shear deformation potentials, the strain‐dependent fundamental band gaps were calculated and shown to be in good agreement with the experimentally measured data within the pseudomorphic limit. The calculated composition‐dependent critical thickness for the onset of plastic deformation of these layers is shown to be in better agreement with the energy balance model of People and Bean than the mechanical equilibrium model of Matthews and Blakeslee.

ISSN:0734-211X    

DOI:10.1116/1.584223

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

(AlAs)1/2(GaAs)1/2fractional‐layer superlattices with a new periodicity perpendicular to the growth direction are successfully grown, by metal–organic chemical vapor deposition on (001) GaAs substrates, slightly misoriented towards [1̄10]. The periodic structure in the lateral [1̄10]direction is analyzed by x‐ray superlattice satellite diffraction and high‐resolution transmission electron microscopy(TEM). Superlattice width along [1̄10] direction are exactly the same as the mean distance of each monolayer step on the (001) vicinal surface. The satellite peak intensity increases with increasing AsH3partial pressure, and is stronger for substrates misoriented towards [1̄10] than those misoriented towards [110]. The result can be explained using the lateral growth model, taking into account the dangling bond at the step edge. The superlattice image is clearly observed by TEM, which shows that the superlattice periods are almost uniform everywhere.

ISSN:0734-211X    

DOI:10.1116/1.584224

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

We report the successful growth of GaAs/AlAs superlattices having interface planes tilted with respect to the substrate surface plane. The amount of tilt and the superlattice period may be controlled by adjusting the growth parameters. The tilted superlattices (TSL’s) were produced by depositing fractional monolayer superlattices (GaAs)m(AlAs)n, withp=m+n≂1, on vicinal (001) substrates. We demonstrate the growth of quantum wirelike structures produced by placing short sections of TSL between horizontal layers of AlAs. Variations of the TSL period and tilt, both on uniform surfaces and on surfaces containing defects, yield insight to the growth kinetics and to the influence of variations in the growth parameters during molecular‐beam epitaxy growth.

ISSN:0734-211X    

DOI:10.1116/1.584225

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

We present evidence that the critical thickness for the appearance of misfit defects in a given material and heteroepitaxial structure is not simply a function of lattice mismatch. We report substantial differences in the relaxation of mismatch stress in Ge0.5Si0.5/Si superlattices grown at different temperatures on (100) Si substrates. Samples have been analyzed by x‐ray diffraction, channeled Rutherford backscattering, and transmission electron microscopy. While a superlattice grown at 365 °C demonstrates a high degree of elastic strain, with a dislocation density<105cm−2, structures grown at higher temperatures show increasing numbers of structural defects, with densities reaching 2×1010cm−2at a growth temperature of 530 °C. Our results suggest that it is possible to freeze a lattice‐mismatched structure in a highly strained metastable state. Thus it is not surprising that experimentally observed critical thicknesses are rarely in agreement with those predicted by equilibrium theories.

ISSN:0734-211X    

DOI:10.1116/1.584226

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Extended fine structures have been observed in the electron energy loss spectrum of InAs. The structures consist of oscillations extending several hundred eV above the InM4,5edge. They are of the type recently observed by others in a variety of materials and are attributed to the same phenomenon responsible for extended x‐ray absorption fine structure (EXAFS); namely, an interference between the outgoing and backscattered parts of the ejected core electron wave function, which in this case is observed as a modulation of the energy distribution of the inelastically scattered electrons above the core edge. Because the backscattering occurs mainly in the near‐neighbor environment of the In atoms and the excitation takes place in the surface region, these oscillations carry surface structural information. We have analyzed the data in the standard EXAFS context and have obtained radial distribution functions for In atoms at the surface of the bulk InAs. The measured nearest‐neighbor distance, uncorrected for the phase shifts, of 2.40±0.04 Å agrees well with the results ofK‐shell EXAFS. This is the first reported measurement of fine structure associated withM‐shell excitations involvingdelectrons.

ISSN:0734-211X    

DOI:10.1116/1.584227

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

We use soft x‐ray photoemission spectroscopy to study the Ga/GaAs and Mn/GaAs interfaces formed at room temperature (RT) and at low temperature (LT=80−100 K). The LT Ga/GaAs interface exhibits the strongly inhibited clustering observed at other nonreactive metal/GaAs interfaces. The Mn–GaAs reaction is slowed somewhat. At both interfaces, the effect of temperature onEFmovement is in accord with the trends previously set: initial band bending onn‐GaAs is slowed at LT, whereas band bending onp‐GaAs is not affected significantly. For both Ga and Mn/GaAs,EFmovement at low coverages is consistent with the explanation proposed for thespand noble metals: introduction of donor states from, e.g., the specific adsorbate levels. Studies of the noble metal interfaces with GaAs have showed that the establishment of the finalEFposition is related to the appearance of metallicity at the interface; Mn/GaAs provides direct evidence for that interpretation.

ISSN:0734-211X    

DOI:10.1116/1.584228

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

We used optical emission techniques to obtain a direct measure of discrete electronic states at GaAs interfaces. These states depend on surface preparation, metallization, and semiconductor material. The energy of the discrete states found at metal/molecular‐beam epitaxially grown GaAs(100) interfaces integrated within a Schottky formalism provides self‐consistent results for the interface electrostatics. The presence of a large concentration of extrinsic defects causes the pinning behavior observed at metal/melt‐grown GaAs(110) interfaces. These results provide the first direct experimental evidence for the origin of Fermi level ‘‘pinning’’ at metal/melt‐grown GaAs junctions.

ISSN:0734-211X    

DOI:10.1116/1.584229

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Schottky barrier formation at metal/n‐GaAs(110) interfaces has been studied with photoemission spectroscopy by varying the substrate doping from 4×1016to 5×1018cm−3. The results challenge certain assumptions that have been made in past barrier formation models. For the clustered systems investigated—In, Ga, and Ag onn‐GaAs— the issue of lateral inhomogeneity of the interface state density is considered. Assuming that the interface states exist only beneath the clusters, lateral variation of the surface potential is expected. An increase of the substrate doping reduces the lateral depletion and should thereby affect this variation. However the core level line shapes exhibit no evidence of an inhomogeneous surface potential for any doping or coverage, even when the depletion length is in the neighborhood of the average cluster spacing. Consequently scenarios are considered in which pinning states are more uniformly distributed than the overlayer material itself. In modeling low‐coverage potential barrier formation, one might suppose that the net interface charge for a given low coverage is independent of the substrate doping. Under this assumption the total band bending for a given coverage is expected to be inversely proportional to the dopant concentration. For the systems examined in this study—In, Ga, Ag, Sn, and Sb onn‐GaAs—an inverse relationship between band bending and doping is observed, but the dependence is much weaker than a proportionality. In the context of a defect model of the interface charge states, this weakened dependence may be explained in terms of a defect state whose nature depends on the local Fermi level position, as has been suggested by Walukiewicz [J. Vac. Sci. Technol. B5, 1062 (1986)]. The effect of metallic screening from the overlayer on the doping dependence of band bending is also considered.

ISSN:0734-211X    

DOI:10.1116/1.584230

出版商:American Vacuum Society    

年代:1988

数据来源: AIP