Pengying Chang

Investigation of Hole Mobility in Strained InSb Ultrathin Body pMOSFETs

Hole mobility in strained ultrathin body InSb-on-insulator (InSb-OI) devices is calculated by a microscopic approach. The anisotropic valence band structures, in consideration of quantum confinement, are obtained via solving the six-band k· p Schrödinger and Poisson equations self-consistently. Hole mobility is calculated using the Kubo-Greenwood formula accounting for nonpolar acoustic and optical phonons, polar optical phonons, and surface roughness scatterings. The models are calibrated and verified with experimental data. The influences of body thickness and strain effect, including both biaxial and uniaxial strains, are investigated in InSb-OI devices. Our results indicate that mobility degradation occurs in both single-gate (SG) and double-gate (DG) mode when body thickness scales down below a certain range. Moreover, mobility in the DG mode outperforms that in the SG for thick body thickness, but loses its superiority over SG for extremely thin body. Compressive strain is favorable to hole mobility. Furthermore, more enhancement is achieved by uniaxial strain than biaxial strain.

An adaptive grid algorithm for self-consistent k·p Schrodinger and Poisson equations in UTB InSb-based pMOSFETs

Hole mobility in ultra-thin body (UTB) InSb-OI devices is calculated by a microscopic approach. An adaptive grid algorithm is employed to discretize 2-D k space. The accurate valence band structures are obtained via solving the 6-band k·p Schrödinger and Poisson equations self-consistently. Hole mobility is computed using the Kubo-Greenwood formalism accounting for nonpolar acoustic and optical phonons, polar optical phonons, and surface roughness scattering mechanisms.

Calculation of the valence band structure in strained In 0.7 Ga 0.3 As devices with different surface orientation

Using the eight-band k·p Hamiltonian approach, the valence band structure of strained In0.7Ga0.3As is calculated for (001), (110) and (111) orientation. The impact of biaxial strain and uniaxial strain on energy band splitting and warping is investigated. The dependency of the valence band structure on the surface electric field and body thickness is also studied in this work.

Strain effects on monolayer MoS2 field effect transistors

In this work, the strain effect on monolayer MoS2 field effect transistors is investigated by density functional (DFT) calculation and quantum transport simulation. DFT calculation reveals that the tensile strain decreases the effective mass, while compressive strain increases the effective mass. However, ballistic quantum transport simulation shows that a smaller effective mass does not always result in better performance for a 5 nm gate length transistor. This is because for field effect transistors in the ultimate scaling region, the suppression of off-state tunneling current is the greatest concern in device design. The effect of scattering is considered by a simple approach and is shown to have a stronger impact on the intrinsic delay for the 10 nm gate length transistor.

Hole mobility enhancements in strained InxGa1%xSb heterostructure p-channel MOSFETs

We explore the use of strain and heterostructure design based on physical modeling to enhance the hole mobility in ultrathin body InxGa1−xSb-based p-channel MOSFETs. The band structure under quantum confinement is calculated by solving the six-band k p Schrodinger and Poisson equations self-consistently. Hole mobility is modeled by the Kubo–Greenwood formula accounting for acoustic and optical phonons, polar optical phonons, surface roughness, and alloy scattering mechanisms. Physical models are calibrated with experimental data. Our results suggest that hole mobility in InxGa1−xSb-based devices increases with increasing InSb mole fraction x, especially under biaxial compressive strain. Mobility markedly deteriorates with the scaling down of body thickness in both unstrained and strained cases. Moreover, an insert of a very thin cap layer with a wide bandgap is helpful to enhance hole mobility. Therefore, greater mobility enhancements are achieved by strained heterostructure optimization.

Hole Mobility in InSb-Based Devices: Dependency on Surface Orientation, Body Thickness and Strain

This work presents an investigation on hole mobility in InSb-based ultra-thin body (UTB) devices with arbitrary surface orientation, body thickness and biaxial strain. The anisotropic band structures with quantum confinement are computed using a fully self-consistent solver for six-band k·p Schrödinger and Poisson equations. Hole mobility is computed using the Kubo-Greenwood formalism accounting for nonpolar acoustic and optical phonons, polar optical phonons and surface roughness scattering. The models are calibrated by fitting the experimental data. Our results suggest that for TB<;10nm, mobility trend with surface orientation and channel directions for InSb devices is: (110)/[T10]>(111)>(110)/[001]>(001), where devices with (111) have more excellent behavior than for Si. In addition, biaxial compressive strain introduces maximum mobility gain in the (110)/[110] case. Nevertheless, (110)/[110] is the optimal surface and channel direction for InSb-based UTB devices, followed by (111) orientation.

Assessment of hole mobility in strained InSb, GaSb and InGaSb based ultra-thin body pMOSFETs with different surface orientations

This work presents a systematic assessment of hole mobility in InSb, GaSb and InGaSb based ultra-thin body (UTB) double-gate pMOSFETs employing a self-consistent method based on 8×8 k · p Schrödinger and Poisson equations and including important scattering mechanisms. Physical models are calibrated against experiments. The effect of body thickness, surface/channel orientation, biaxial and uniaxial strain, and heterostructure design on hole mobility in III-V materials has been systematically investigated in order to help in providing useful guidelines.

Strain effects on valence band structure of In 0.7 Ga 0.3 As: From bulk to thin film

Strain effects on valence band structure in bulk and thin film In0.7Ga0.3As was presented, including in-plane biaxial and uniaxial stress. The impact on energy band splitting and warping, and effective mass are evaluated by 6×6 k·p method. The dependence of the valence band structures on the body thickness was also studied.

Investigation of scattering mechanism in nano-scale double gate In 0.53 Ga 0.47 As nMOSFETs by a deterministic BTE solver

We investigate the scattering mechanism in ultrashort double gate In0.53Ga0.47As nMOSFETs by deterministically solving Boltzmann transport equation (BTE). The intra-valley acoustic phonon scattering, optical phonon scattering, intervalley optical scattering, polar optical scattering, and surface roughness (SR) scattering are considered. The impacts of scattering on the performance of device under high/low biases are compared. Results show that the ballistic ratio (Iscat/Iball) decreases from 96.8% to 94.5% when the drain bias increases from 0.05V to 0.6V, which is mainly caused by the inter-valley scatterings.