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Determination of the Valence Band Offset in GaAs/(Ga,Al)As Superlattices by Hot Electron Excitation Spectroscopy
Published online by Cambridge University Press: 22 February 2011
Abstract
A GaAs/Ga1−xA1xAs-superlattice was investigated using quasi-cw PL measurements at T=2 K. The relevant sample parameters were determined by X-ray diffraction: barrier thickness - 5 nm, qw-thickness - 5 nm, x = 0.41. A series of PL-spectra at medium, but constant excitation intensity for different excitation energy (from 1.64 eV to 2.1 eV) was measured. From the high-energy slope of the PL-spectra the electron-temperature Te was determined. A clearly structured dependence of Te on hvexc (excitation energy) was found. We assumed the pronounced structures of the Te - hvexc - hvexc - “spectrum” to be the onset-energies of new, for lower excitation energies not possible relaxation processes. Calculating the excess energy for each kind of carriers (heavy and light holes and electrons) separately, we found δEv=( 0.18 ± 0.05) ∆Eg for the investigated sample. Using this new experimental method one also is able to obtain the energies of higher electronic states (for example Γ → L -transitions) of GaAs/(Ga,Al)Assuperlattices.
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- Copyright © Materials Research Society 1993