strain [110]
Fig. 4.7 Optical phonon scattering rate for uniaxial compressive strain with ε=
-0.5% in the [100] (dash line) and [110] (dot line) directions, compared with unstrained case (solid line).
1 10 100
Fig. 4.8 Hole drift velocity as a function of the electric field applied along [100]
direction for two uniaxial compressive strain cases, ε= 0, and -0.5%.
The uniaxial compressive strain direction is the channel direction. The low field mobility is extracted in the inset.
0 1 2 3
0.0 -0.1 -0.2 -0.3 -0.4 -0.5 400
500 600
M o bil ity (cm 2 /v*sec)
strain (%) [100]
[110]
Fig. 4.9 Calculated hole mobility versus uniaxial compressive stress along [100]
and [110] directions.
Chapter 5 Conclusions
Two kinds of valence band structure models are studied. A Monte Carlo simulation is developed to calculate hole transport properties, such as hole mobility and drift velocity. Moreover, the difference of the simulation results with the bond orbital model and with the Luttinger-Kohn model is also examined. Furthermore, the hole drift velocities along [100] and [110] channel directions are also calculated, and the simulation results show the weak anisotropy of the drift velocity.
The strain effect on hole mobility is also evaluated with the Luttinger-Kohn model. And our simulation results show that the hole mobility enhancement can be obtained with uniaxial compressive strain. And it draws a lot of interest to apply compressive strain in [110] direction due to its larger mobility enhancement.
Finally, a Monte Carlo program is established to simulate the carrier transport properties. The strain effect on the device performance, such as mobility and saturation velocity can be examined by a Monte Carlo program, which will becomes a powerful simulation tool for device simulation in the next generation.
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