S. A. Clark

Observation of photoluminescence from InAs surface quantum wells grown on InP(100) by molecular beam epitaxy

Photoluminescence (PL) measurements are presented for thin epitaxial layers of InAs, 2.5 A<d <36 A, grown on InP(100) by molecular beam epitaxy. The combination of efficient carrier capture and PL redshift with increasing InAs thickness clearly indicate the formation of InAs quantum wells on the InP surface. Data are also presented for InAs/InP structures capped with strained layers of either GaAs or In0.5 Al0.5 As. Since radiative recombination within the InAs layers can be distinguished from PL arising from both bulk and surface defects, this system allows us to monitor the quality of both the InAs/InP and InAs/air interfaces via their influence on the InAs quantum well luminescence.

Influence of the composition modulation on the relaxation of In0.54Ga0.46As strained layers

TEM observation of In0.54Ga0.46As grown by MBE on InP shows a coarse tweed quasiperiodic structure related with a composition modulation. The period Λ of this modulation has been found to be dependent on the layer thickness. The elastic energy associated with the modulation induced strain, has been taken into account to explain this period dependence. The evolution of strain parallel to growth surface with epilayer thickness has been correlated with both the change on the modulation period and the presence of defects.

Admittance spectroscopy of InAlAs/InGaAs single‐quantum‐well structure with high concentration of electron traps in InAlAs layers

Results are presented of admittance spectroscopy measurements on the lattice‐matched In0.52Al0.48As/In0.53Ga0.47As single‐quantum‐well structures. It has been found that the perpendicular conductivity of the structure is controlled by the strong temperature dependence of the space‐charge region width around the quantum‐well layer. This process is governed by a high density of deep electron traps present in the layers adjacent to the quantum well. Therefore, the energy activation of perpendicular conductivity is determined by the deep‐level defects rather than the thermionic emission of electrons from the quantum well. Because of this, it is impossible to extract the magnitude of the band offset between the quantum well and barrier layers from the admittance measurements performed in this study.

Strain relaxation studied by photoluminescence and by double crystal X-ray diffraction measurements in strained InGaAs

Photoluminescence (PL) and double crystal X-ray diffraction (DCXD) experiments have been carried out on strained View the MathML sourceAs grown on InP substrate by molecular beam epitaxy with different epilayer thicknesses, in order to study lattice relaxation. Samples with tensile strain (View the MathML source) and compressive strain (View the MathML source) have been investigated. Strain was measured by DCXD in conjunction with detailed rocking curve analysis within a dynamical framework. From PL results, we have evaluated the strain values in two different ways. First, we used the PL transition shift induced by strain and second, from PL temperature dependence we measured the heavy-hole-light-hole splitting, which is a direct measurement of strain. Our results have shown good agreement between PL and DCXD measurements and also the existence of residual strain even in samples with a thickness considerably greater than the critical layer thickness.

An investigation of the electrical and chemical properties of intimate metal‐InyAl1−yAs(100) interfaces

The electrical and chemical properties of the interfaces formed at room temprature, between the surface of epitaxial n‐type InyAl1−yAs(100) and a selection of metals have been studied. Highly ideal Au, Ag, Cu, and In diodes exhibiting the highest reported barriers (0.78–0.91 eV), measured by the current‐voltage (I‐V) technique, have been obtained by forming intimate contacts on atomically clean, lattice matched, molecular beam epitaxy grown InyAl1−yAs/InP(100). The formation of Au‐ and In‐InyAl1−yAs interfaces has been investigated using x‐ray photoemission spectroscopy, showing that in both cases the Fermi level is pinned at the surface prior to metal deposition. The deposition of both In and Au overlayers initiated the selective removal of As from the interface to segregate on the metal surface; however the presence of these metals on the semiconductor surface produced no further Fermi shift. These observations, in conjunction with the barrier heights measured by the I‐V technique, are discussed in the ...

Growth by molecular beam epitaxy of thick films of InxGa1−xAs (x ≈ 0.53) on Si(100) substrates

Thick films of InxGa1−xAs (x = 0.53 ± 0.04) have been grown on misoriented silicon substrates by molecular beam epitaxy as a function of substrate temperature and layer thickness. For films of 3 μm thickness, grown in the temperature range Tg = 200 to 550°C, the films became increasingly rough as the growth temperature was raised and the full width at half maximum of the double crystal X-ray diffraction features were very broad (more than 1000 arc s). In most cases these diffraction features were symmetric, but for growth in a small temperature window around 350°C highly asymmetric peaks were observed due to variations in the tilt angle between the (100) lattice planes of the substrate and epitaxial layer. The magnitude and direction of the tilt angle were found to be highly dependent on growth temperature being directed away from the substrate normal for Tg around 350°C but towards the substrate normal for higher substrate temperatures. A variable thickness study performed at 350°C showed that the maximum tilt angle increases approximately linearly with thickness, reaching a value of about 7500 arc s for layers 8 μm thick.

Photoluminescence study of the 2D electron gas formed at the interface of strained InGaAs/InP single heterostructures

Photoluminescence measurements have been performed in two series of strained InxGa1-xAs/InP single heterostructures, grown by molecular beam epitaxy with different epilayer thicknesses. Tensile strained samples (xIn = 0.508) and compressive strained samples (xIn = 0.543) have been investigated. An emission 30 meV below the excitonic recombination has been observed in these structures and we ascribe it to a recombination between photocreated holes and electrons from the two-dimensional electron gas formed at the InGaAs/InP interface. The role of the epilayer thickness on the photoluminescence recombination mechanism of the two-dimensional electron gas is discussed. Measurements of the photoluminescence temperature dependence have revealed the heavy-hole and light-hole splitting in this emission. The value of this splitting is in very good agreement with the expected values obtained by double crystal X-ray diffraction measurements.

Surface InAs/InP quantum wells: epitaxial growth and characterization

The epitaxial growth and characterization of InAs surface quantum wells grown on InP by molecular beam epitaxy (MBE) are discussed. The structural properties of the InAs layers are described. Photoluminescence results are presented. This system shows practically no coupling between the confined states in the InAs quantum well and the InAs surface states.<<ETX>>