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Article

Abstract

The effect of the gate leakage current fluctuations on noiseproperties of AlGaN/GaN heterostructurefield effect transistors(HFETs) has been studied in conventional HFET structures and in AlGaN/GaN metal-oxide-semiconductorheterostructurefield effect transistors (MOS-HFETs). The comparison of the noiseproperties of conventional AlGaN/GaN HFETs and AlGaN/GaN MOS-HFETs fabricated on the same wafer, allowed us to estimate the contribution of the gate currentnoise to the HFET’s output noise. The effect of the gate current fluctuations on output noiseproperties of HFETs depends on the level of noise in the AlGaN/GaN HFETs. For the transistors with a relatively high magnitude of the Hooge parameter α∼10−3, even a relatively large leakage currentIg (Ig/Id∼10−3–10−2, where Idis the drain current) does not contribute much to the output noise. In HFETs with a relatively small values of α (α∼10−5–10−4), the contribution of the leakage current to output noise can be significant even at Ig/Id∼10−4–10−3. For such transistors, a very rapid increase of the 1/fnoise with gate bias was observed. The differences in the noise behavior can be linked to the material quality of the AlGaN and GaN layers in different types of HFETs.

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