Discussion Forum

Hi,

I am trying to make an electro-thermal GaN-HEMT device model on Comsol using the Semiconductor and Heat Transfer modules.

I have tried to incorporate the Caughey-Thomas mobility model to evaluate field dependent mobility at high drain voltages (Vds). However, I could not succeed in predicting the experimental data accurately. Therefore, I have decided to manually input a field-dependent mobility expression (known as Canali model). For that purpose, I need to make "Electric field parallel to electron current density" an input to my user defined expression.

When I activate the Caughey-Thomas mobility model (mmct), this particular parameter is automatically calculated by Comsol. Its variable name is: comp1.semi.smm1.mmct1.Epn. In the Caughey-Thomas Mobility tutorial, it is possible to plot the variable as it is readily evaluated.

However, when mmct is not used/activated, this parameter is not recognized by Comsol.

How can I evaluate this parameter in terms of the existing variables in the Semiconductor module? I have been focusing on writing a summation of dot products of J and unit vectors and taking the squareroot of that expression. However, I could not yet find the correct parameters.

I appreciate if you could share your experience or ideas on this.

Thanks, Bugra