Abstract
In this work, a Wheatstone bridge-type pressure sensor based on AlGaN/GaN heterostructure was fabricated for the first time. The pressure sensor consisted of four gateless high electron mobility transistors (HEMTs) on a 585 μm depth circular membrane, in which 15-μm-thick silicon substrate was left. Direct voltage readout was realized in the AlGaN/GaN pressure sensor, which exhibited a non-linearity of 0.6% with a sensitivity of 1.25 μV/kPa/V over a wide pressure range from 0.1 MPa to 5 MPa. Because of the in-plane isotropic properties, the working mechanism in the AlGaN/GaN pressure sensor is found to be quite different from the silicon-based sensor. Although the resistances of the four gateless HEMTs all increased with enlarging pressure, the changes of neighboring resistors varied with alignments under the piezoelectric effects. Finally, voltage linear readout was realized by the differential operation of Wheatstone bridge circuit.
Highlights
Attributed to the excellent piezoelectric properties, high mechanical and chemical stability, AlGaN/GaN heterostructures are very attractive for the pressure sensing applications in harsh environment where silicon based sensors cannot operate.[1]
The channel current showed nonlinear variation to the pressure in the proposed pressure sensor based on AlGaN/GaN high electron mobility transistor (HEMT),[7,8] which could not be convenient for direct pressure sensing
The AlGaN/GaN heterostructure used for gateless HEMTs based Wheatstone-bridge pressure sensors is grown by metal organic chemical vapour deposition (MOCVD) on a 600-μm-thick silicon (111) substrate.[15]
Summary
Attributed to the excellent piezoelectric properties, high mechanical and chemical stability, AlGaN/GaN heterostructures are very attractive for the pressure sensing applications in harsh environment where silicon based sensors cannot operate.[1]. AlGaN/GaN pressure sensor with a Wheatstone bridge structure Observable changes of channel conductivity happened under different stress conditions.[4,5,6] the channel current showed nonlinear variation to the pressure in the proposed pressure sensor based on AlGaN/GaN high electron mobility transistor (HEMT),[7,8] which could not be convenient for direct pressure sensing.
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