Structural and electronic properties of group III Rich In0.53Ga0.47As(001) (original) (raw)
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Optik, 2017
There are kinds of reconstructions on InGaAs(100) surface, such as As-rich  2 (2 × 4), In-rich ␣(2 × 4), and Ga-rich ␣(2 × 4) reconstructions. In this article, the three kinds of In 0.53 Ga 0.47 As(100) reconstruction surfaces are studied based on first-principles calculations, and atomic structures, formation energies, band structures, electron distributions, and absorption coefficients were obtained. Atomic structures of the surfaces were calculated and results show that the relaxation of As-rich  2 (2 × 4) surface is the smallest. The As-rich  2 (2 × 4) surface also has the smallest formation energy, which means the As-rich  2 (2 × 4) surface is the steadiest among the three surfaces. Furthermore, the energy band structures and the work function are analyzed. The less the work function is, the easier the photoelectrons escape from the surfaces. Therefore, it is the easiest for photoelectrons to escape from As-rich  2 (2 × 4) surface due to its lowest work function. The same conclusion is also confirmed based on the calculations of the electronic structure. The negative electron affinity photocathode is mainly sensitive to the infrared region where the absorption coefficient of the As-rich  2 (2 × 4) surface is bigger than those of the In-rich ␣(2 × 4) and Ga-rich ␣(2 × 4) surfaces. The As-rich  2 (2 × 4) surface is benefit for the formation of the negative electron affinity In 0.53 Ga 0.47 As photocathode.
Physical Review B, 2003
Using an ab initio plane-wave-pseudopotential code we study a variety of 3ϫ1 and 3ϫ2 reconstructions including adatom ͑A͒, dimer ͑D͒, and interstitial ͑I͒ models of Ge, Si, and diamond͑113͒ surfaces. All reconstruction elements give rise to local minima on the total-energy surface. For Ge and Si, interstitial reconstructions are confirmed to be most favorable. Reconstructions without interstitials, even the oppositely puckered 3ϫ2 AD model, do not open a surface-state gap. The semiconducting 3ϫ2 ADI structure is the lowest one in energy for Si, since the occupied surface states appear below the valence-band maximum. The 3ϫ2 AI surface with asymmetric pentamers is also semiconducting and, in the Ge case, it is even lower in energy. The 3ϫ1 AD model is found to be the most stable ͑113͒ surface reconstruction for diamond, despite the vanishing gap. The measured structural data, the observed ͑in particular occupied͒ surface states, the scanning-tunneling microscopy images of Si and Ge(113)3ϫ2 and 3ϫ1 surfaces, as well as the temperature-induced phase transitions can widely be explained using models with subsurface interstitial atoms and accounting for the mobility of such atoms.
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2002
More than two decades ago it was shown that the surface barrier of In x Ga 1Ϫx As alloys, positive, in depletion, and negative, in accumulation passes through zero at, or near, xϭ0.8. Consequently, the energy bands at the surfaces of In 0.8 Ga 0.2 As might be the same as in the bulk; i.e., at flatband. Electrical, galvanomagnetic, and surface photovoltage measurements made on transistor-like, gated, eight-arm, In 0.8 Ga 0.2 As metal-insulator-semiconductor structures confirm that the equilibrium surface Fermi level is, indeed, at flatband. Although the density of surface states is of the order 10 12 /cm 2 applied gate voltages can displace, quasistatically, the Fermi level, from above the conduction band edge to the vicinity of the valence band edge. An interpretation of the data applied to this as well as to all of the other In x Ga 1Ϫx As alloys is based on Zunger's ''vacuum pining rule'' and Walukiewicz's Fermi level stabilization energy. The energies of the states which determine their surface barriers are not referred to their conduction and valence band edges. Instead, they are amphoteric charged defects located on a composition-independent reference level, located ϳ4.95 eV below the vacuum level.
Physical Review B, 2003
Ab initio density-functional-theory-local-density-approximation electronic structure calculations are performed for the InAs͑110͒ surface and compared with scanning tunnel microscopy ͑STM͒ measurements using the Tersoff-Hamann model. In both, calculations and measurements, we see the same atomic features. At negative and small positive energies, the local density of states is concentrated around the As atom, while at higher positive energies it is centered above the In atom, because of the appearance of the In dangling bond. Moreover, we describe two types of irregular STM images on the InAs͑110͒ surface. First, we measure dI/dV images exhibiting atomic resolution at voltages within the band gap, which, however, still can be understood within the Tersoff-Hamann model as due to a higher-order term. Second, we measure features on the subatomic scale with certain tips at low tip-sample distance, which are most likely caused by elastic interactions between the tip and the surface.
Atomic layer diffusion and electronic structure at In[sub 0.53]Ga[sub 0.47]As/InP interfaces
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2004
We have used secondary ion mass spectrometry and cathodoluminescence spectroscopy to determine the effects that growth and postgrowth conditions have on interdiffusion and near band edge emissions in In 0.53 Ga 0.47 As/InP heterojunctions grown by molecular beam epitaxy. This lattice-matched interface represents a model system for the study of atomic movements and electronic changes with controlled anion overlap during growth. Structures subjected to anneals ranging from 440 to 495°C provide a quantitative measure of concentration-driven cross diffusion of group-III and group-V atoms. By measuring anneal-induced broadening at the InGaAs-on-InP interface we have determined an activation energy for As diffusion into InP of ϳ2.44Ϯ0.40 eV. An interface layer with GaP bonds indicates Ga competes favorably versus As for bonding in the preannealed InP near-surface region. In addition, we present evidence that interface chemical effects manifest themselves electronically as variations of the InGaAs band gap energy.
Fermi-level pinning and intrinsic surface states in cleaved GaP
Physical Review B, 1989
The electronic structure of Al 1Àx In x Nð10 10Þ surfaces is investigated by cross-sectional scanning tunneling spectroscopy and density functional theory calculations. The surface exhibits empty Al and/or In-derived dangling bond states, which are calculated to be within the fundamental bulk band gap for In compositions smaller than 60%. The energy of the lowest empty In-derived surface state is extracted from the tunnel spectra for lattice-matched Al 1-x In x N with In compositions of x ¼ 0.19 and x ¼ 0.20 to be E C À 1.82 6 0.41 and E C À 1.80 6 0.56 eV, respectively, in good agreement with the calculated energies. Under growth conditions, the Fermi level is hence pinned (unpinned) for In compositions smaller (larger) than 60%. The analysis of the tunnel spectra suggests an electron affinity of $3.5 eV for nonpolar lattice-matched Al 1-x In x N cleavage surfaces, which is large compared to linearly interpolated values of polar AlN and InN (0001) surfaces.
Origin of surface and subband states at the InAs(111)A surface
Physical Review Materials
The atomic structure of surfaces and interfaces plays a vital role in the electronic quality and properties of quantum devices. The interplay between the surface and confined bulk subband states in terms of their susceptibility has been investigated in relation to crystal defects on an InAs(111)A-(2 × 2) reconstructed surface, using low-temperature scanning tunneling microscopy and spectroscopy. We measure the two-dimensional quantized subband states arising from the confined potential imposed by downward bending of the conduction band edge. Furthermore, we show evidence of the existence of surface Bloch states within the confined bulk band gap projected on the surface spectrum which have originated from the surface reconstruction. As expected, larger confined bulk band gaps at the surface and conduction band offset are measured to be 0.58 and 0.31 eV, respectively. We further show the scattering of these quantum states at different surface defects and demonstrate that surface states are more susceptible to the defect potential when compared with the corresponding subband states. This apparent contrast follows from the length scale at which these defect potentials actively interact on or near the surface. Our observed experimental results are supported by empirical tight-binding simulations for the subband states and first-principles density functional theory simulations for the surface states present on the surface.
Structure of the In-rich InAs (001) surface
Surface Science, 2012
Using scanning tunneling microscopy, frequency-modulated scanning atomic-force microscopy, electron diffraction, and density functional theory calculations we investigate a structure of the InAs (001) surface displaying c(8 × 2)/(4 × 2) reconstruction at room temperature. It is found that the room temperature data are satisfactorily interpreted based on the model proposed by Kumpf et al. [Phys. Rev. Lett. 86, 3586 (2001)], however, at cryogenic temperatures the model fails since a different structure, characterized by fourfold period along [110] crystallographic direction, partial disorder and instability, is observed. By the present study we find that the structure is described by corrected Kumpf et al. model where most of atomic rows are left as in the original model and only the dominant indium atom rows running along [110] are changed. At room temperature the dominant rows are disordered and rapidly fluctuate thermally while at cryogenic temperatures they convert to chains of indium aggregates and acquire fourfold period. Moreover, frequently observed incomplete occupancy of the dominant indium rows leads to many different local surface structures, reflected by characteristic "features" in scanning tunneling microscopy patterns. We have classified and explained most of these structures.
Surface Science, 2002
The structure of InAs(0 0 1)-ð2 Â 4Þ surfaces equilibrated under typical MBE conditions is studied by scanning tunneling microscopy (STM). Depending on the magnitude of the As flux, typical surfaces are found to contain a mixture of a2ð2 Â 4Þ and b2ð2 Â 4Þ reconstructions. The relative populations of the a2 and b2 reconstructions are found to depend on substrate temperature and the magnitude of the As flux. The atomic-scale details of the reconstructed units on these mixed-phase surfaces are definitively determined by comparing atomic-resolution dual-bias STM images to first-principles calculations. The imaging mechanism for revealing atomic-scale details, particularly the trench dimer, is found to be qualitatively similar to that for GaAs, although the effect is less pronounced. Additionally, a significant population of ad-atom related structures are observed on quenched surfaces, apparently unrelated to any equilibrium ad-atom population. Ó 2001 Published by Elsevier Science B.V.