GaN HEMT Thermal Optimization using Flip Chip structure

ganfetex14.in : GaN HEMT Thermal Optimization using Flip Chip structure

Requires: Blaze
Minimum Versions: Atlas 5.28.1.R

This example demonstrates two-dimensional electro-thermal simulations with heat sink structures.

Although the superiority of GaN HFET device characteristics has been demonstrated, the self heating effect has hindered the production of high power and high speed GaN-based switching devices. This effect can be significantly reduced by the cost effective heat-sink approach. in this EXAMPLE, in order to understand and control the self heating effect, GaN HFET with flip chip concept is simulated, and device characteristics are compared versus normal structure using Atlas.

For HFETs, the GaN/AlGaN epitaxial layers have been grown on either sapphire or SiC substrates. Although sapphire has the advantage of lower cost and availability in larger wafer sizes, its poor thermal conductivity (0.3 W/cm-K) limits the achievable powers due to severe self-heating. The self heating effect can be significantly reduced by flip-chip mounting the devices onto highly conducting substrates such as AlN (1.8 W/cm-K).

The typical GaN HFET flip chip structure in this example is a Al0.25Ga0.75 N-GaN HFET on a sapphire substrate. The structure consists of an AlN layer as a heat sink, a 2.7nm undoped AlGaN layer, and 2 GaN layers which includes 20nm doped 1e15 GaN and 1um undoped GaN.

The self-heating is a local increase of crystal temperature due to dissipated Joule electric power, this effect can significantly reduce the electron mobility and degrade device performance.

DC, Transient and AC simulations are done and compare with and without the flip chip structure. As expected the performance of the device is better when lattice temperature is reduced.

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.