The objectives of this investigation are structural and physical characteristics of the n-Sii_Ge/n(p)-Si heterojunction under strong elastic deformation of Si1_Ge layers which gives rise to misfit dislocations in the heteroboundary region; the factors playing the main role in formation of the band structure of the system; the use of transmission electron microscopy and optical methods for determination of the phenomena connected with misfit dislocations in the grown epitaxial structure; the electrical characteristics of diode structures and the process of electron-hole recombination via dislocation states in a heterojunction.
The low-temperature electrical and magnetotransport characteristics of partially relaxed Si/Si 1-x Ge x heterostructures with two-dimensional electron channel (n e ≥ 10 12 cm -2 ) in an elastically strained silicon layer of nanometer thickness have been studied. The detailed calculation of the potential and of the electrons distribution in layers of the structure was carried out to understand the observed phenomena.The dependence of the tunneling transparency of the barrier separating the 2D and 3D transport channels in the structure, was studied as a function of the doping level, the degree of blurring boundaries, layer thickness, degree of relaxation of elastic stresses in the layers of the structure. Tunnel characteristics of the barrier between the layers were manifested by the appearance of a tunneling component in the current-voltage characteristics of real structures. Instabilities, manifested during the magnetotransport measurements using both weak and strong magnetic fields are explained by the transitions of charge carriers from the two-dimensional into three-dimensional state, due to interlayer tunneling transitions of electrons.
We report on the first attempt to fabricate arrays of one-dimensional quantum wires from 2D layer In x Ga 1-x As/GaAs structures, based on a self-organization concept. A decrease in the dimensionality of the electron-hole gas in the objects of interest, which is due to a 2D to 1D electron subsystem transformation in the layers of this structure, is detected by the shift and narrowing of the PL spectral lines.Porous semiconductor materials that under electrochemical etching of a crystal provide a convenient medium for fabricating reduced dimensionality objects like two-dimensional planes [1, 2], quantum wires [3], and tunnel chains of quantum zero-dimensional grains [4,5] have recently become a subject of increasing interest. One way of creating a system of quantum wires is to fill the pores of a dielectric "host crystal" [3, 6] until a new chemical compound of a metal (Bi) or semiconductor (PbTe) type of conductivity is formed. In this work we discuss another approach to fabricate quantum wire arrays, which is based on the idea of their self-organization in the process of electrolytic etching of multilayer heteroepitaxial structures that contain nanometer-thick layers with a 2D electron-hole gas, built into these structures during the epitaxial growth. For the "host crystal" we used epitaxial single and multilayer, including periodic semiconductor heterostructures, i.e., GaAs/In x Ga 1-x As grown on GaAs (100) semi-insulating substrates, which were thoroughly studied elsewhere [7]. In x Ga 1-x As layers in the original samples formed single or double quantum wells; these layers were doped with a donor impurity from 10 15 to 10 16 cm -3. The total number N of quantum-size In x Ga 1-x As layers in the structures varied from 1 to 10. Brief information about the content (x) and the thickness of In x Ga 1-x As layers in quantum well structures (QWS) is presented in Table 1. Here d qw is the thickness of a single quantum well, d b is the thickness of the barrier in a double quantum well, x is the In content in the In x Ga 1-x As layer, d 1 = 2d qw + d b is the total thickness of a double quantum well. The double quantum wells were spaced in the GaAs crystal at about 0.07 µm [7].Our technique of forming 1D conductor arrays consisted in etching the oblique channels in a crystal, which intersect the planes of In x Ga 1-x As nanometer-thick layers built into the GaAs crystal. Electrochemical etching of samples was a standard operation performed in an alcoholic solution of hydrofluoric acid at the current densities of 20-40 mA/cm 2 under UV radiation. Etching of an In x Ga 1-x As/GaAs (100) structure is most likely to proceed along oblique channels in the (111) direction [1].
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