Magneto-optical investigations of a novel superlattice: HgTe-CdTe
TL;DR: In this article, a quasi zero-energy-gap semiconductor superlattice was investigated and the offset between the HgTe and CdTe valence bands was determined in terms of interband transitions from valence to conduction subbands.
Abstract: Far-infrared magnetoabsorption experiments done in a HgTe-CdTe superlattice are presented. From the results, which are interpreted in terms of interband transitions from valence to conduction subbands, the superlattice band structure has been deduced. These investigations show, in particular, that this superlattice is a quasi zero-energy-gap semiconductor, and yield the first determination of the offset between the HgTe and CdTe valence bands.
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TL;DR: In this paper, the authors present a survey of new theoretical models of semiconductor heterojunctions and illustrate their newfound ability to derive from first principles rules of heterojunction behavior.
390 citations
IBM1
TL;DR: In this article, a tight-binding theory of semiconductor heterojunction band lineups is presented, where interface dipoles play a crucial role in determining lineups, so that lineups obtained by using the vacuum level as a reference (e.g., the electron affinity rule) are not reliable.
Abstract: A tight-binding theory of semiconductor heterojunction band lineups is presented. Interface dipoles are shown to play a crucial role in determining lineups, so that lineups obtained by using the vacuum level as a reference (e.g., the electron affinity rule) are not reliable. Instead, the self-consistent lineup can be obtained approximately by aligning the average sp 3 hybrid energies in the respective semiconductors. Numerical results are provided and compared with experiment, and the approximations and accuracy in this approach are discussed. The application of these ideas to Schottky barriers is also considered.
201 citations
TL;DR: In the inhomogeneous structure, which is the contact of two semiconductors with mutually inverted bands, two-dimensional non-degenerate electron states exist as discussed by the authors, and these states appear due to the supersymmetry of an effective Hamiltonian and do not depend on the specific form of the transition region.
133 citations
TL;DR: In this article, the authors present an overview of several theoretical approaches and experimental measurement techniques for determining band offset values and discuss the experimental and theoretical data reported for a number of specific heterojunction systems.
Abstract: Publisher Summary This chapter presents an overview of several theoretical approaches and experimental measurement techniques for determining band offset values and discuss the experimental and theoretical data reported for a number of specific heterojunction systems. It also evaluates the credibility and accuracy of the experimental measurements and provides a tabulation of reliable band offset values for as many heterojunctions as possible. Among the most important physical parameters for a given heterojunction system are the conduction- and valence-band offsets; indeed, the quality and even the feasibility of heterojunction device concepts often depend crucially on the values of these band offsets. The band offset is defined simply as the discontinuity in the band edge at the interface between two semiconductors. A number of current theories seem to yield band offset values in reasonable agreement with experiment, even though the physical ideas underlying these theories can be quite different. These ideas include electron affinities, Schottky barrier heights, bulk band structures on the same energy scale, and the definition of effective midgap energies corresponding to charge neutrality for each bulk constituent.
116 citations
TL;DR: In this article, the authors determine the band alignments within the polycrystalline Cu(In1−xGax)(Se1−ySy)2 semiconductor system using the energy position of the dominant acceptor state as a reference level.
Abstract: The composition dependence of defect energies in polycrystalline Cu(In1−xGax)(Se1−ySy)2 chalcopyrite thin films is investigated by admittance spectroscopy of ZnO/CdS/chalcopyrite heterojunctions. We determine the band alignments within the polycrystalline Cu(In1−xGax)(Se1−ySy)2 semiconductor system using the energy position of the dominant acceptor state as a reference level. Upon alloying CuInSe2 with S the activation energy of the acceptor increases from 300 meV to approximately 380 meV in CuIn(Se0.4S0.6)2. A similar result holds when using Cu(In1−xGax)(Se1−ySy)2 with x≈0.3. In contrast, the acceptor activation energy remains essentially unchanged in the Cu(In1−xGax)Se2 alloy system over the whole composition range 0⩽x⩽1. Taking the acceptor energy as reference, we find a valence band offset ΔEV=−0.23 eV between CuInSe2 and CuInS2. The same valence band offset is found between Cu(In0.7Ga0.3)Se2 and Cu(In0.7Ga0.3)S2. In contrast, the combination CuInSe2/CuGaSe2 displays ΔEV below 0.04 eV. Our results indicate that a bulk reference level exists in the Cu(In1−xGax)(Se1−ySy)2 semiconductors which sets the band structure on a common energy scale, thus establishing the natural band lineups within the alloy system automatically. This conclusion is sustained by our finding that the position of the Fermi level at the CdS/chalcopyrite interface exhibits a constant energy distance to the acceptor level. The concentration of bulk acceptors is in addition correlated to the open circuit voltage losses of heterojunction solar cells.
108 citations