The incapability of the drift-diffusion model to demonstrate and predict the physics-based phenomenon in the advance node devices, poses lot of issues. The predicted current-voltage characteristics of these devices through drift-diffusion model are not reliable. The drift-diffusion models are valid, in general, for large devices dimensions geometries, where applied electric field is not so high to causes the mobility degradation and where the quantum confinement effect can be ignored. The modified drift-diffusion model with inclusion of field dependent mobility models and diffusion coefficients extends its validity up to a certain level of device dimensions when carrier velocity overshoot is negligible. The drift-diffusion model is popular for conventional device modeling relying under the assumption of equilibrium transport conditions; however, at high biasing conditions the results obtained from drift diffusion model also differed significantly even in big dimensional geometry devices due to the prominent ballistic transport effects.
TNL-PD simulator, a particle device simulator (PDS). It uses ensemble Monte Carlo (EMC) technique for the solution of the Boltzmann transport equation coupled with quantum confinement effects, whereas 2D Poisson equations is solved through successive over relaxation (SOR) method with the inclusion of different non-linear scattering mechanisms. It is also equipped with parallel computing feature to minimize the simulation time. TNL-PD (particle device) simulator considers the transport of Monte Carlo particles (also known as super particles) with or without inclusion of the quantum confinement effects under influence of applied external field, determined self-consistently through the solution of coupled Poisson's and BTE equation over a suitably small time-step on the electronic band structure. The time step is taken typically less than the inverse plasma frequency obtained with the highest carrier density in the device. The Poisson equation solution (V) is generated over the 2D-node points on the meshes. The carrier transport solution is obtained in 3D using ensemble Monte Carlo (EMC) on the full range of space coordinates (few valleys or full electronic band structure) in accordance with the particle distribution itself.
During scattering mechanisms, the energy of carrier remains conserved which is termed as Fermi-Golden rule. For carrier kinetic energies less than about 1.0eV, scattering occurs at a sufficiently low rate to satisfy the Uncertainty Principle and validate the semi-classical approach.
The particle-mesh coupling method is a widespread technique for space charge calculations. The spatial distribution of potential and electric field is obtained through solution of Poisson equation in TNL Particle Device Simulator (TNL-PDS) for simulation of semiconductor devices with Monte Carlo (MC) technique. The accurate computation of particle dynamics under applied electric field requires accurate solution of Poisson’s equation.
Two boundary conditions, the reflective boundary conditions are implemented in the simulator Neumann condition while the carriers hit the contact region of the device where carrier absorb and immediately re-emitted from same contact with different wave vector or from other contact to follow carrier conservation principle inside the device, Dirichlet boundary condition.
The 2D and 3D Poisson solution with tracking the super-particle in all three dimensions real space and momentum space is always cost-effective solution for advance and conventional node device technologies i.e. MOSFET, MESFET, FDSOI, TunnelFET, HEMT etc with the static and transient I-V characteristics.
The quantum confinement effect in the TNL-PD simulator: explain quantization effects in modern down-scaled microelectronics devices through density gradient model, Bohm quantum potentail and effective potential approach.
Optical device characterization: through propagation and absorption program integrated into the TNL PDS framework. The monochromatic and polychromatic sources with optical intensity profiles can be defined by using TNL Optical Source frame. The selected light illuminates the semiconductor device either from top or bottom edges. The intensity profiles are then converted into photo generation rates, which are directly integrated into the generation terms in the carrier distribution function in Boltzmann transport equation. The unique coupling of optical characterization tool allows user to simulate electronic responses against optical signals for a broad range of optical detectors and solar cells applications.
