Control of Current Collapse in Thin Pattern GaN

Technology #18476

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William Gallagher
Marinus Hopstaken
Ko-Tao Lee
Professor Tomas Palacios
Department of Electrical Engineering and Computer Science, MIT
External Link (
Daniel Piedra
Department of Electrical Engineering and Computer Science, MIT
Devendra Sadana
Managed By
Christopher Noble
MIT Technology Licensing Officer - Clean and Renewable Energy
Patent Protection

Control of Current Collapse in Thin Pattern GaN

US Patent Pending 2016-0225887


High electron mobility transistors (HEMTs) are suitable for high power, high frequency and/or high temperature applications.

Problem Addressed

HEMT efficiency is limited by a current collapse phenomena in Gallium Nitride (GaN) metal-semiconductor field effect transistors.  Current collapse occurs when the GaN on-resistance increases and current decreases during the application of high voltage to the device. Pronounced current collapse (40% or greater) in C-doped GaN HEMTs is observed when the GaN buffer layer is < 2 microns. This technology uses metal organic chemical vapor deposition (MOCVD) to create a patterned region between GaN and the substrate to reduce current collapse.  


This technology uses a silicon on insulator (SOI) substrate. During co-integration of GaN with 200 mm hybrid SOI, patterned regions are created such that <111> Si is exposed.  The depth and coverage of the patterned region cannot exceed 1.5 µm  and 50%, respectively, because it will create large stresses during GaN growth on  the Si. The SOI substrate thickness is typically in the range of 725-775 µm and corresponds to that used by Si CMOS industry. The invention demonstrates how the current collapse can be reduced to <10% even with <1.5 µm GaN HEMT structure in the patterned region.  


  • Reduces current collapse
  • Improves HEMT performance