Showing papers on "Magnetocapacitance published in 1990"

Magnetoresistance and Magnetocapacitance in a Two-Dimensional Electron Gas in the Presence of a One-Dimensional Superlattice Potential

Abstract: A novel type of magnetoresistance oscillation is observed in a two-dimensional electron gas in a high mobility GaAs-AlGaAs heterostructure with a holographically induced lateral periodic modulation in one direction The modulation arises due to the persistent photoconductivity of the samples at low temperatures The experiments show that the 1/B periodicity of the additional oscillations is determined by the carrier density N s and the period a of the grating, reflecting the commensurability of cyclotron diameter and modulation period The key to the explanation of the novel magnetotransport oscillations is an oscillatory linewidth of the modulation broadened Landau bands To demonstrate this we have performed magnetocapacitace measurements in order to obtain direct information about the density of states of the modulated two-dimensional electron gas

The Investigation of Single and Double Barrier (Resonant Tunnelling) Heterostructures Using High Magnetic Fields

Abstract: This chapter examines some important properties of single and double barrier tunnelling heterostructures. Particular emphasis is placed on the use of magnetic fields in studying not only the tunnelling process itself, but also the way in which electrons relax their energy and momentum. Four topics are examined in detail. First, LO phonon-related oscillations under reverse bias in the I(V) and C(V) curves of single barrier n +GaAs/(A1Ga)As/n −GaAs/n +GaAs and n +(InGa)As/Inp/n −(InGa)As/n +(Inga)As heterostructures are explained by the variation of the impedance of the undepleted section of the n − layers. For the GaAs/(A1Ga)As/GaAs structure, a magneto-impurity resonance at 5 T is observed in the oscillation amplitude, indicating that the impedance variation is due principally to impact ionisation of donors, rather than to LO phonon ionisation. The apparently anomalous behaviour of the magnetocapacitance in these devices in reverse bias is also accounted for. In the reverse-biased (InGa)As/InP/(InGa)As structures, the oscillations in I(V) have period ΔV = 33 meV, indicating that the electron energy relaxation occurs almost exclusively via Ga — As mode LO phonons of the n −(InGa)As layer.