502 CHAPTER 10. COHERENT TRANSPORT AND MESOSCOPIC DEVICES
10
8
6
4
2
0
Gate length
0.25μm–2 –1.8 –1.6 –1.4 –1.2 –1
GATE VOLTAGE (V)
C
ONDUCTANCE(2
(^2) e
/h
)
AlGaAs––––
GaAs- GaAs EC
Figure 10.10: Experimental studies on conductance fluctuations arising in a GaAs/AlGaAs chan-
nel constricted by the structure shown. The results are for the channel conductance in units of
e^2 /π(=2e^2 /h). (From the paper by B. J. van Wees, et al., Phys. Rev. Lett., 60 , 848 (1988).)
Figure 10.11: SEM image of a single electron transistor (SET) structure. Figure courtesy of
Greg Snyder, University of Notre Dame.
10.5.2 Coulomb Blockade Effects ......................
So far in our discussion we have not paid attention to the Coulombic repulsion between elec-
trons. The reason is that in large systems the repulsion is negligible. However, in very small