TCAD Examples

ganfetex15.in : GaN HEMT BV versus Gate to Drain distance

Requires: Blaze
Minimum Versions: Atlas 5.28.1.R

This example demonstrates the influence of the Gate to Drain distance on the breakdown voltage with and without silicon substrate. This example is based on the following reference

Experimental and simulation study of breakdown voltage enhancement of AlGaN/gaN heterostructures by Si substrate removal. D.Visalli et al Apl. Phys. Lett. 97, 113501 2010.

The structure consists of 20nm AlGaN with xcomp=0.2 and 1um GaN buffer layer. Donor and acceptor traps are included in the simulation. Gaussian profile acceptor traps are used with a peak concentration close to the bottom of the buffer layer to mimic the fact that the material quality improves toward the surface of the device.

Donor Interface traps at the AlGaN/Nitride interface and acceptor interface traps at the GaN/Silicon interface are also included during the simulation.

Forward charateristic simulation reveals a threshold voltage of around -2V. Slow transient simulation is used to simulate the breakdown voltage curve.

The deck is parametrized so that we can make variation of the distance between gate and drain (LGD). Deckbuild DoE capability is used to automate simulations of BV versus LGD with and without substrate.

We can observe in tonyplot an almost linear increase of BV versus LGD when silicon substrate is not present. An increase of the gate current is observed near breakdown and the value is of the same order as the drain current. This result indicates that BV is defined by an avalanche phenomenon between the gate and the drain.

BV does not depend significantly on LGD when silicon substrate is present due to charge accumulation at the GaN/Silicon interface, related to the presence of interface traps, which screen the electric field. During the simulation and for comparison purpose, a resistance is added to the substrate so that the current leakage through the substrate is reduced. Note that if no resistance is added to the substrate an increase of the substrate current is observed near breakdown and the value is of the same order as the drain current. This result indicates that BV is defined by an avalanche phenomenon between the gate and the substrate in this case.

To load and run this example, select the Load button in DeckBuild > Examples. This will copy the input file and any support files to your current working directory. Select the Run button in DeckBuild to execute the example.