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6CCVD Research

Measuring the thermal conductivity of the GaN buffer layer in AlGaN/GaN HEMTs - Effect of carbon and iron doping

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2015-05-01
AuthorsMĂĄire Power, James W. Pomeroy, Yohei Otoki, Takeshi Tanaka, Jiro Wada
InstitutionsUniversity of Bristol, Hitachi (Japan)

Abstract

Section titled “Abstract”

Introduction and purpose of work During operation, AlGaN/GaN high electron mobility transistors (HEMTs) exhibit a temperature rise in the active GaN region of the device which affects reliability and performance. One of the main determining factors of this temperature rise is the thermal conductivity of the GaN active layer which is often assumed to be 150-160 Wm -1 K -1 [1] in thermal simulations in order to estimate the peak channel temperature rise in the device. However, there is little experimental validation of the actual thermal conductivity (Îș) of transistor epitaxial GaN layers which may be dependent on the dopants used and their concentrations such as, for example, carbon (C) doping [2] for power transistors or iron (Fe) doping [3] for microwave transistors. The temperature gradient within the GaN layer is required to verify the thermal conductivity of this layer and therefore verify the peak channel temperature estimation in reliability studies. This abstract describes a novel technique combining diamond microthermometry and micro-Raman thermography to determine the temperature gradient within the carbon-doped (concentration of 10 17 cm -3 ) GaN layer of an AlGaN/GaN ungated HEMT. Diamond micro-thermometry and micro-Raman thermography measure the surface temperature and average temperature depth-wise of the GaN layer respectively with the difference in these temperatures related to the temperature gradient. Utilising finite element thermal simulation the thermal conductivity of the GaN layer was determined. This value was used in the thermal modelling of an AlGaN/GaN HEMT of the same epilayer structure to validate the peak channel temperature estimation of the transistor. The work also aims to discuss the impact of carbon and iron-doping on the thermal properties of AlGaN/GaN HEMTs.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

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