Tutorial

Welcome to the openbandparams tutorial. This will teach you the basics. If you have not already installed openbandparams, please see Installation. First, start up an interactive python shell:

$ python

Next, import everything from the openbandparams package:

>>> from openbandparams import *

Now you can access the materials and their properties:

>>> GaAs
GaAs
>>> InAs
InAs
>>> InSb
InSb

The lattice constant, in units of Angstroms (Å), is accessed like this:

>>> GaAs.a()
5.65325

The bandgap, in units of electron Volts (eV), is accessed like this:

>>> GaAs.Eg()
1.4224821428571428

Some parameters depend on temperature. If the temperature is not provided, it defaults to 300 Kelvin:

>>> GaAs.Eg(T=300)
1.4224821428571428
>>> GaAs.Eg(T=0)
1.519

There are many parameters available:

>>> GaAs.Eg_Gamma()
1.4224821428571428
>>> GaAs.Eg_X()
1.898857142857143
>>> GaAs.Eg_L()
1.7069642857142857
>>> GaAs.meff_e_Gamma()
0.067

A full list of parameters available for a given material can be printed using the following one-liner:

>>> sorted([p.name for p in GaAs.get_unique_parameters()])
['CBO', 'CBO_Gamma', 'CBO_L', 'CBO_X', 'Delta_SO', 'Eg', 'Eg_Gamma',
'Eg_Gamma_0', 'Eg_L', 'Eg_L_0', 'Eg_X', 'Eg_X_0', 'Ep', 'F', 'VBO', 'a',
'a_300K', 'a_c', 'a_v', 'alpha_Gamma', 'alpha_L', 'alpha_X', 'b',
'beta_Gamma', 'beta_L', 'beta_X', 'c11', 'c12', 'c44', 'd',
'electron_affinity', 'luttinger1', 'luttinger2', 'luttinger3',
'luttinger32', 'meff_SO', 'meff_e_Gamma', 'meff_e_Gamma_0',
'meff_e_L_DOS', 'meff_e_L_long', 'meff_e_L_trans', 'meff_e_X_DOS',
'meff_e_X_long', 'meff_e_X_trans', 'meff_hh_100', 'meff_hh_110',
'meff_hh_111', 'meff_lh_100', 'meff_lh_110', 'meff_lh_111',
'nonparabolicity', 'thermal_expansion']

A description of any parameter can easily be printed:

>>> print GaAs.Eg.description
bandgap energy

For documentation of the parameters, see Supported Parameters.

Ternary alloys are also supported:

>>> AlGaAs(x=.3)
AlGaAs(Al=0.3)
>>> AlGaAs(Al=.3)
AlGaAs(Al=0.3)
>>> AlGaAs(Ga=0.7)
AlGaAs(Al=0.3)
>>> AlGaAs(Al=0.3).Eg()
1.840788343373494

As of version 0.8, you must follow the alloy naming scheme. Group III elements come first, with the lowest atomic number elements first, followed by the Group V elements, also ordered by atomic number:

>>> GaInAs
GaInAs
>>> GaPAs
GaPAs

If you reverse the element order, an error will be raised to let you know:

>>> InGaAs
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'InGaAs' is not defined
>>> GaAsP
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'GaAsP' is not defined

Ternaries can be lattice matched to a desired lattice constant using the following syntax:

>>> GaInP(a=GaAs.a())
GaInP(Ga=0.516340648855)
>>> GaInP(a=GaAs.a()).Eg()
1.9259077529765196

In the previous example, a lattice matching temperature of 300 K is assumed. To lattice match to a different lattice matching temperature use the following syntax:

>>> GaInP(a=GaAs.a(), T=300)
GaInP(Ga=0.516340648855)
>>> GaInP(a=GaAs.a(), T=400)
GaInP(Ga=0.523158422221)

Instancing can be used to get multiple parameters from an alloy:

>>> GaInP_on_GaAs = GaInP(a=GaAs.a(), T=300)
>>> GaInP_on_GaAs
GaInP(Ga=0.516340648855)
>>> GaInP_on_GaAs.Eg(T=300)
1.9259077529765196
>>> GaInP_on_GaAs.Eg(T=77)
2.010415191481605
>>> GaInP_on_GaAs.a()
5.653250000000166

The same concepts also apply to quaternaries:

>>> GaInPAs(P=0.1, a=InP.a(), T=300)
GaInPAs(Ga=0.4176, P=0.1)
>>> GaInPAs(P=0.1, a=InP.a(), T=300).Eg()
0.8237397670939017
>>> myGaInPAs = GaInPAs(P=0.1, a=InP.a(), T=300)
>>> myGaInPAs.Eg()
0.8237397670939017
>>> myGaInPAs.a()
5.869700012767527

It’s also possible to get a LaTeX representation of the alloy:

>>> GaInPAs.latex()
'Ga_{x}In_{1-x}P_{y}As_{1-y}'
>>> GaInPAs(P=0.1, a=InP.a(), T=300).latex()
'Ga_{0.4176}In_{0.5824}P_{0.1}As_{0.9}'

Now that you have the basics down, check out the Examples to see what’s possible.