Will the velocity of GaN HEMTs ever overshoot?

Yifeng Wu, Bobby Brar, Lester Eastman, Jasprit Singh, Arvydas Matulionis, Bob Trew, Umesh Mishra, Ilesanmi Adesida

Research output: Contribution to journalConference articlepeer-review


As the result of recent rapid development in advanced device designs, the power density of GaN HEMTs has rocketed to >30 W/mm at C and X bands, a level exceeding what was predicted for diamond devices. While this is almost beyond what even the high thermal conductivity of the SiC substrates can handle, it is a good problem to have. However, the GaN HEMT has been performing poorly at millimeter-wave bands. A major hurdle is that the cut-off frequencies do not scale up well with the shrinkage of gate length. Traditionally, the electron velocity of III-V FETs overshoots as the gate length reduces to sub-micron scale, which overcomes the higher percentage of parasitic charging times as the intrinsic input capacitance reduces. This overshoot is not yet seen in GaN HEMTs. What is worse, the ft of these devices peaks at only 25-30% of the full-channel current and deteriorates severely at higher current levels. These problems are responsible for the measly 2-5 W/mm and 15-40% efficiency produced by GaN HEMTs at >30 GHz. So, what is limiting the speed of the GaN HEMT? Will its electron velocity ever overshoot? What will be the best power device at millimeter-wave frequencies. Please join the discussion on the future of ultra-high speed power electronics.

Original languageEnglish (US)
Pages (from-to)191
Number of pages1
JournalDevice Research Conference - Conference Digest, DRC
StatePublished - 2004
Externally publishedYes
EventDevice Research Conference - Conference Digest, 62nd DRC - Notre Dame, IN, United States
Duration: Jun 21 2004Jun 23 2004

ASJC Scopus subject areas

  • Engineering(all)


Dive into the research topics of 'Will the velocity of GaN HEMTs ever overshoot?'. Together they form a unique fingerprint.

Cite this