Hints, Tips and Solutions

Q. Can Atlas be used to simulate advanced III-V or II-VI materials ?

A. Yes. ATLAS now supports a wide range of materials in its database. This database covers single elememt conductors, binary compounds and quaternary compounds. A complete list of all materials can be found in Appendix B of the ATLAS Users Manual Vol. II.

It should be noted however, that many of these materials are quite recent and do not have a comprehensive set of physical parameters or physical models yet available. ATLAS can still be used to simulate these devices but requires three contributions from the user.

First, the user should ensure that a complete set of physical parameters are available. To illustrate this the material InAlAs will be invoked within an input deck. To check the required physical parameters are available before a simulation is started the following command should be written within the input deck

MODEL PRINT

This will then produce in the runtime output window of deckbuild the following table when two regions are present, GaAs and InAlAs :

REGIONAL MATERIAL PARAMETERS:
Region : 1 2
Material : GaAs InAlAs
Type : semicond. semicond.
Epsilon : 13.2 0

BAND PARAMETERS
Eg (eV) : 1.42 2.1
Chi (eV) : 4.07 0
Nc (per cc) : 4.35e+17 1
Nv (per cc) : 8.16e+18 1
ni (per cc) : 2.12e+06 2.29e-18
Gc : 2 2
Gv : 4 4
Ed (eV) : 0.044 0.044
Ea (eV) : 0.045 0.045

RECOMBINATION PARAMETERS
Lifetime (el): 1e-09 1
Lifetime (ho): 2e-08 1
Auger cn : 5e-30 0
Auger cp : 1e-31 0
Auger kn : 0 0
Auger kp : 0 0
Copt : 1.5e-10 0
An** : 6.29 110
Ap** : 105 30

IMPACT IONIZATION MODEL PARAMETERS (SELBERHERR MODEL)
betan : 1.82 1
betap : 1.75 1
egran : 0 0
an1 : 1.9e+05 8.6e+06
bn1 : 5.75e+05 3.5e+06
an2 : 1.9e+05 8.6e+06
an2 : 5.75e+05 3.5e+06
ap1 : 2.22e+05 2.3e+07
bp1 : 6.57e+05 4.5e+06
ap2 : 2.22e+05 2.3e+07
bp2 : 6.57e+05 4.5e+06

SATURATION VELOCITIES
Vsatn (cm/s) : 7.7e+06 1e+06 1e+06
Vsatp (cm/s) : 7.7e+06 1e+06 1e+06

As shown, the material InAlAs does not have certain parameters predefined such as epsilon and Chi. The user is required to define these parameters, all the Band Parameters and any Recombination and Impact Ionization Parameters required in the model definitions. In this case the necessary ATLAS statement could be:

material material=InAlAs permittivity=13.9 nc300=1.5e17 nv300=8.1e18 affinity=3.6 eg300=1.47 taun0=1.2e-9 taup0=1.2e-9

Second, the physical parameters inbuilt into ATLAS/Blaze cover GaAs, AlGaAs, InGaASP, SiGe and SiC. For advanced materials either constants values need to be used or the C-interpreter is required. For instance, the bandgap in these materials is a function of either the x or y or both mole fractions. If a graded mole fractions is required in a device the user has to use the C-interpreter to define the variation of bandgap with the x or y mole fraction.

Third, there are a limited set of physical models available within ATLAS/Blaze, such as for mobility. The C-interpreter should therefore be applied by the user to define relevent and accurate physical models for the material they are studying.

 

Call for Questions

If you have hints, tips, solutions or questions to contribute, please contact our Applications and Support Department
Phone: (408) 567-1000 Fax: (408) 496-6080
email: support@silvaco.com