NJTT: Near Junction Thermal Transport

Many defense semiconductor power amplifiers (PAs) and other high-power electronic and photonic components are thermally limited by the high thermal resistance of the region within 100 µm of the electronic junction, also known as the near junction region. 

The goal of the Near Junction Thermal Transport (NJTT) effort of the TMT program is to achieve a 3x or greater improvement in power handling from GaN power amplifiers through improved thermal management of the near junction region. This will benefit the warfighter by increasing the capability of RF systems such as Radar, communications and Electronic Warfare.

To reduce the near junction thermal barrier, NJTT approaches include:

• The use of high thermal conductivity diamond substrates, replacing lower conductivity materials such as SiC, Si, and Sapphire.
• The removal by etching or other techniques of low conductivity epitaxial and transition layers at the interface of the GaN and the substrate.
• The introduction of liquid cooling in the near-junction region.
• Additionally, NJTT has a strong focus in both metrology and modeling to address the challenges of measurement verification at this scale and quantifying thermal and electrical performance of the GaN devices.

These approaches will increase the power handling capability without interfering with the present operation of the PA. 

A successful NJTT effort will provide technologies for improved device-level thermal management for GaN PAs, as well as a number of relevant electronic and optical systems of interest to the DoD.