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Journal of Electronic Materials

, Volume 42, Issue 1, pp 10–14 | Cite as

Polarization-Engineered Ga-Face GaN-Based Heterostructures for Normally-Off Heterostructure Field-Effect Transistors

  • Hyeongnam Kim
  • Digbijoy Nath
  • Siddharth Rajan
  • Wu LuEmail author
Article

Abstract

Polarization-engineered Ga-face GaN-based heterostructures with a GaN cap layer and an AlGaN/p-GaN back barrier have been designed for normally-off field-effect transistors (FETs). The simulation results show that an unintentionally doped GaN cap and p-GaN layer in the buffer primarily deplete electrons in the channel and the Al0.2Ga0.8N back barrier helps to pinch off the channel. Experimentally, we have demonstrated a normally-off GaN-based field-effect transistor on the designed GaN cap/Al0.3Ga0.7N/GaN channel/Al0.2Ga0.8N/p-GaN/GaN heterostructure. A positive threshold voltage of 0.2 V and maximum transconductance of 2.6 mS/mm were achieved for 80-μm-long gate devices. The device fabrication process does not require a dry etching process for gate recessing, while highly selective etching of the GaN cap against a very thin Al0.3GaN0.7N top barrier has to be performed to create a two-dimensional electron gas for both the ohmic and access regions. A self-aligned, selective etch of the GaN cap in the access region is introduced, using the gate metal as an etch mask. The absence of gate recess etching is promising for uniform and repeatable threshold voltage control in normally-off AlGaN/GaN heterostructure FETs for power switching applications.

Keywords

Normally-off III-nitride heterostructures polarization engineering selective etching GaN cap AlGaN/p-GaN back barrier 

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Copyright information

© TMS 2012

Authors and Affiliations

  • Hyeongnam Kim
    • 1
  • Digbijoy Nath
    • 1
  • Siddharth Rajan
    • 1
  • Wu Lu
    • 1
    • 2
    Email author
  1. 1.Department of Electrical and Computer EngineeringThe Ohio State UniversityColumbusUSA
  2. 2.Department of Nanobio Materials and ElectronicsGwangju Institute of Science and TechnologyGwangjuSouth Korea

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