Source code for simudo.materials.germanium

from math import pi
from simudo.physics import Material



class GermaniumMaterial(Material):
    '''Germanium material data based on Palankovski.

       V. Palankovski and R. Quay, "Analysis and Simulation of Heterostructure Devices",
       Springer-Verlag (2004).
    '''

    name = 'Germanium'



    def get_dict(self):
        d = super().get_dict()
        U = self.unit_registry

        d.update({
            # Static dielectric constant, Palankovski Table 3.3
            'poisson/permittivity': U('16.0 vacuum_permittivity'),

            # Table 3.9
            # These X value are for strained Ge on Si, not bulk Ge. Used for interpolating alloys.
            'CB/EgX_0K': U('0.57 eV'),
            'CB/ChiX_0K': U('4.199 eV'),
            'CB/EgL_0K': U('0.7437 eV'),
            'CB/ChiL_0K': U('4.0253 eV'),
            'CB/varshni_alphaL': U('4.774e-4 eV/K'),
            'CB/varshni_betaL':  U('636 K'),

            # Table 3.21
            'CB/MCL': U('4'),

            # Table 3.18
            'CB/mL': U('0.222'),
            'CB/m1n': U('0.0068'),

            # Table 3.19
            'VB/m0p': U('0.28'),
            'VB/m1p': U('0.1'),
            'VB/m2p': U('0.0'),

            'CB/SRV': U('4000 cm/s'),
            'VB/SRV': U('4000 cm/s'),

            'SRH/CB/tau':   U('1e-9 s'),
            'SRH/VB/tau':   U('1e-6 s'),

            # Properties for band-to-band tunneling
            'CB/eff_mass_tunnel': U('0.05'),
            'VB/eff_mass_tunnel': U('0.1'),
            'CB/tunnel_offset_energy': U('0 eV'),
            'VB/tunnel_offset_energy': U('0 eV')
        })

        T = self.temperature
        Eg  = d['CB/EgL_0K']  - d['CB/varshni_alphaL'] * T**2 / (d['CB/varshni_betaL'] + T)
        Chi = d['CB/ChiL_0K'] + d['CB/varshni_alphaL'] * T**2 / (d['CB/varshni_betaL'] + T)

        mn = d['CB/mL'] + d['CB/m1n'] * (T / U('300 K'))
        mp = d['VB/m0p'] + d['VB/m1p'] * (T / U('300 K')) + d['VB/m2p'] * (T / U('300 K'))**2

        NC = 2 * d['CB/MCL'] * (2 * pi * mn * U.electron_mass * U.boltzmann_constant * T / U.planck_constant**2)**(3/2)
        NV = 2 * (2 * pi * mp * U.electron_mass * U.boltzmann_constant * T / U.planck_constant**2)**(3/2)

        d.update({
            'CB/mDOS': mn,
            'VB/mDOS': mp,
            'CB/energy_level': -Chi,
            'VB/energy_level': -Chi -Eg,
            'CB/effective_density_of_states': NC,
            'VB/effective_density_of_states': NV,

            # TODO - update these from Palankovski
            'CB/mobility': U('1400 cm^2/V/s'),
            'VB/mobility': U(' 450 cm^2/V/s'),

            'SRH/energy_level': -Chi -Eg/2

        })

        return d