Abstract
Dielectric layers prepared by different deposition methods were used for the surface passivation of AlGaN/GaN heterostructure field-effect transistors (HFETs) and the corresponding electrical characteristics were examined. Increases in the sheet charge density and the maximum drain current by approximately 45% and 28%, respectively, were observed after the deposition of a 100 nm-thick SiO2 layer by plasma-enhanced chemical vapor deposition (PECVD) on the top of the AlGaN/GaN HFETs. However, SiO2 deposited by a radio frequency (rf) sputter system had the opposite effect. As the strain applied to AlGaN was influenced by the deposition methods used for the dielectric layers, the carrier transport in the two-dimensional electron gas formed at the interface between AlGaN and GaN was affected accordingly.
Highlights
We investigated the effect of dielectric layers on the carrier transport properties in AlGaN/GaN heterostructure field-effect transistors (HFETs) by using two different deposition techniques for the SiO2 layer
The sheet carrier density for the Sputter-SiO2 sample is slightly decreased by 8% from that for the reference; the density is increased by 45% for the plasma-enhanced chemical vapor deposition (PECVD)-SiO2 sample
Dielectric layers prepared by two different deposition methods of PECVD and rf-sputtering for the surface passivation of AlGaN/GaN HFETs were investigated
Summary
An AlGaN/GaN heterostructure field-effect transistor (HFET), among the potential nextgeneration power devices, has many advantageous intrinsic properties, including high efficiency, frequency, and power.[1,2,3] These advantages are enabled by the high mobility and sheet carrier density of the two-dimensional electron gas (2DEG) layer formed naturally at the interface between AlGaN and GaN.[4,5] The sheet carrier density in the 2DEG is influenced by many factors such as the thickness, Al mole fraction, and the spontaneous and piezoelectric polarization of the AlGaN layer.[6,7,8] In addition, it is known that the surface state of AlGaN is sensitive to the atmosphere, which affects the carrier density of the 2DEG.[9]. We investigated the effect of dielectric layers on the carrier transport properties in AlGaN/GaN HFETs by using two different deposition techniques for the SiO2 layer.
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