First-principles study of electronic properties of biaxially strained silicon: Effects on charge carrier mobility

Abstract

Using first-principles method, we calculate the electronic band structure of biaxially strained silicon, from which we analyze the change in electron and hole effective mass as a function of strain and determine the mobility of electrons and holes in the biaxially strained silicon based on Boltzmann transport theory. We found that electron mobility increases with tensile strain and decreases with compressive strain. Such changes are mainly caused by a strain-induced change in electron effective mass, while the suppression of intervalley scattering plays a minor role. On the other hand, the hole mobility increases with both signs of strain and the effect is more significant for compressive strain because the hole effective mass decreases with compressive strain but increases with tensile strain. The strain-induced suppression of interband and intraband scatterings plays also an important role in changing the hole mobility.

Bending induced electrical response variations in ultra-thin flexible chips and device modeling

“…The hole mobility increases with both tensile and compressive biaxial strain and is more pronounced in the case of compressive strain. 123,148 These observations do not depend on the channel direction. The value of the shear piezocoefficient (P 66 ) in biaxially strained (001) p-type Si has been shown to increase for compressive biaxial strain and decrease in the case of a tensile strain.…”

“…148 On the other hand, in p-type Si the heavy-hole (HH) and light-hole (LH) valence bands minima are degenerated at the C point in the absence of stress as shown in Fig. 7(d).…”

“…123 The resistors and MOSFETs have been extensively studied to determine the variation of mobility of electrons and holes with biaxial stress and to analyze the electronic band structure of biaxially strained-Si. 148,149 These studies show that the electron mobility increases with tensile biaxial strain and decreases with compressive strain. The hole mobility increases with both tensile and compressive biaxial strain and is more pronounced in the case of compressive strain.…”

Mobility enhancement of strained Si transistors by transfer printing on plastic substrates

“…33,34 The roll-based transfer approach of a strained Si layer can effectively provide important benefits to the development of high-performance strained Si TFTs for large-area flexible electronic applications. [15][16][17]35 Figure 4a shows the key fabrication steps for a strained Si TFT array on a flexible PET film using an automated roll transfer method.…”

“…The degree of this enhancement agrees well with the theoretical calculation based on the electronic properties of biaxially strained silicon (Figure 5d and Supplementary Note S6). 34 The performance of strained Si TFT would be saturated at 40% with a higher level of tensile strain. 40 In addition, the enhanced mobility and threshold voltages exhibit a similar tendency as the channel length increased from 10 to 30 μm (Supplementary Figures S13 − S15).…”