Infrared Excitations in Electronic Systems with Reduced Dimensionality
Modern semiconductor devices are increasingly based on structure in which the electronically active channel is an electron or hole system with reduced dimensionality. The classical example is the metal-oxide-semiconductor-field-effect-transistor (MOSFET) in which electrons can be confined at the semiconductor-oxide interface to form a quasi-two-dimensional electron system (2DES). Another more recently developed device is the high-electron-mobility transistor (HEMT) in which a suitable doping profile induces a 2D electron channel at the heterojunction potential barrier. The extraordinary electronic properties of such two-dimensional electron systems at interfaces are summarized in part in an extended review by Ando, Fowler and Stern1. Fig. 1 schematically pictures the band diagram in the confinement direction perpendicular to the interface for both devices. In the MOS-system (Fig. 1a) a positive gate voltage Vg is applied between the p-type semiconductor and the metal gate and causes bending of the conduction and valence bands near the semiconductor-oxide interface. The electrons are confined in a narrow potential well bounded by the oxide barrier and the conduction band edge. In the modulation doped heterojunction (Fig. 1b) n-type doping of the large gap semiconductor (e.g. AlxGa1-x As) causes electron transfer to the undoped p-type lower gap semiconductor (e.g. GaAs) with a larger electron affinity.
KeywordsCyclotron Resonance Landau Level Inversion Layer Lower Landau Level Gate Voltage Versus
Unable to display preview. Download preview PDF.
- 11.J. P. Kotthaus, Infrared spectroscopy of lower dimensional electron systems, Physica Scripta, in press.Google Scholar
- 14.A.D. Wieck, Ph. D. thesis, University of Hamburg 1987, unpublished.Google Scholar
- 24.U. Merkt, Spectroscopy of inversion electrons on III–V semiconductors, in: “Festkörperprobleme: Advances in Solid State Physics”, Vol. 27, P. Grosse, ed., Vieweg, Braunschweig (1987).Google Scholar
- 30.Batke, W. Hansen, D. Heitmann, J. P. Kotthaus, U. Mackens, L. Prager and K. Ploog, Lateral structures of submicron periodicity on Si-MIS-systems and AlGaAs-GaAs heterojunctions, in: “Semiconductors, Quantum Well Structures, and Superlattices”, K. Ploog and N. T. Linh., eds., Edition des Physique, Les Ulis (1986).Google Scholar
- 31.Wassermeier, H. Pohlmann and J. P. Kotthaus, Magnetoconductivity of inversion electrons in periodic MOS-microstructures on Si, in: “The Physics of Semiconductors”, O. Engströni, ed., World Scientific, Singapore (1987).Google Scholar
- 32.P. Kotthaus, W. Hansen, H, Pohlmann, M. Wassermeier and K. Ploog, Intersubband resonances in quasi-one-dimensional channels, Surf, Sci., to be published.Google Scholar
- 33.Merkt, C. Sikorski and J. P. Kotthaus, Spectroscopy of one-dimensional subbands on InSb, Superlattices and Microstructures, to be published.Google Scholar
- 34.Hansen, J. P. Kotthaus, A. Chaplik and K. Ploog, Electronic excitations in laterally microstructured AlGaAs-GaAs heterojunctions, in: “The Application of High Magnetic Fields in Semiconductor Physics”, G. Landwehr, ed., Springer, Heidelberg (1987).Google Scholar
- 36.T. Zettler and J. P. Kotthaus, to be published.Google Scholar