Magnetic modulations of optical and transport properties of N-doped coupled double quantum wells Page: 4 of 6
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(a) (b) (c)
B11 11 x
-
L L L L uL
1=0 B11>w 0, low T Biw 0, high T
Figure 1. Anticrossing in symmetric DQWs and
the transitions from the upper (U) and lower (L)
branches.
2 B11-Evolution of the PL Spectraa--
z
-J
Or
W
W
CC
1s.~LUMNESCENCE
ENERGY (eV)
Figure 2. B1-evolution of the PL spectra from
sample 1 for Btu from 0 to 9 T.Eq. (1) is solved using a self-consistent density functional theory including the
Hartree and exchange-correlation potentials [2]. The PL spectra are calculated using
the formalism of Ref. 3 and assuming that the damping Fis constant independent of
the energy and is the same for the electrons and holes. The PL spectra are
determined by the square of the wave function overlap times the joint spectral
density of the electrons and the photogenerated holes averaged over their occupation
probabilities given by the Fermi-Dirac and Boltzmann distributions.
The theory is applied to symmetric DQWs (sample 1) with 100 A wells, a 35 A
center barrier, and 100% ionized delta dopants inside the outer barriers at a distance
50 A from the outer interfaces with a density 1.2X10/cm2 each. Calculated PL
spectra are displayed in Fig. 2 for 0 - B11 5 9 T [4]. The spectra have two peaks at
low Bt's. The upper peak (U) disappears at 5 T. The U-peak appears to be stronger
because it rests at the tail of the lower peak (L). The double to single peak behavior
can be understood from Fig. 1: at B11 =0, two strong PL peaks U and L arise from ky
= 0 area near the bottoms of the upper and lower branches. At B11 = 5 T, however, U
disappears because the holes are depopulated from the ky = 0 area. At a higher
temperature, U disappears at a higher Bu as seen from Fig. 1(c).
Figures 3 and 4 display the anticrossing and the PL spectra for asymmetric
DQWs (sample 2) with the same structure as sample 1 but with a total electron
density 6.0X10"'/cm2 and a 6 kV/cm electric field. In this case, the holes are in the
right QW. The U peak is strong at Bu = 0 and arises from the intrawell transitions
inside the right QW as illustrated in Fig. 3(a). The L peak arises from the interwell
transitions and is weak. At, high Bu's, the U peak becomes weak because the holes
are not available and is replaced by a strong L peak as seen from Figs. 3(c) and 4.
The behavior in Fig. 2 and 4 is consistent with recent observation [5].page 2/4
T=4 K -
r=1.O meV
9.0
.0
5.0
U 1.0
L 0.0.
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Lyo, S.K.; Simmons, J.A.; Huang, D. & Harff, N.E. Magnetic modulations of optical and transport properties of N-doped coupled double quantum wells, article, August 1, 1998; Albuquerque, New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc702086/m1/4/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.