Abstract
Wide bandgap gallium nitride (GaN)-based devices have attracted a lot of attention in optoelectronics, power electronics, and sensing applications. AlGaN/GaN based sensors, featuring high-density and high-mobility two-dimensional electron gas (2DEG), have been demonstrated to be effective chemical sensors and biosensors in the liquid environment. One of the key factors limiting the wide adoption of the AlGaN/GaN liquid sensor is the package reliability issue. In this paper, the reliability of three types of sensor packaging materials (SiO2/Si3N4, PI, and SiO2/Si3N4/PI) on top of 5-μm metal are tested in Phosphate buffer saline (PBS) solution. By analyzing the I-V characteristics, it is found that the leakage currents within different regimes follow distinct leakage models, whereby the key factors limiting the leakage current are identified. Moreover, the physical mechanisms of the package failure are illustrated. The failure of the SiO2/Si3N4 package is due to its porous structure such that ions in the solution can penetrate into the packaging material and reduce its resistivity. The failure of the PI package at a relatively low voltage (<3 V) is mainly due to the poor adhesion of PI to the AlGaN surface such that the solution can reach the electrode by the “lateral drilling” effect. The SiO2/Si3N4/PI package achieves less than 10 μA leakage current at 5 V voltage stress because it combines the advantages of the SiO2/Si3N4 and the PI packages. The analysis in this work can provide guidelines for the design and failure mechanism analysis of packaging materials.
Highlights
Since the ion-sensitive field-effect transistor (ISFET) concept was proposed by P
PI to the AlGaN surface such that the solution can reach the electrode by the “lateral drilling” effect
The most essential distinction between the AlGaN/gallium nitride (GaN) based sensors and the conventional HEMT power electronic devices is the working environment, while HEMT power electronic devices operate in ambient conditions, AlGaN/GaN based liquid sensors are expected to perform in a solution environment
Summary
Since the ion-sensitive field-effect transistor (ISFET) concept was proposed by P. Gallium nitride is a wide-bandgap (WBG) semiconductor material that is desirable and promising because of its superior material properties such as its chemical inertness, thermal stability, high electron concentration and high mobility in the heterojunction two-dimensional electron gas (2DEG) channel [2]. The high electron density and high electron mobility in the 2DEG channel can deliver high sensitivity of the sensor. AlGaN/GaN based sensor, the drain and source terminals are located on the chip surface along with the gate, which is immobilized with the sensitive membrane for selective detection, including the pH of the solution [3,4], ions [5,6,7], DNA [8,9,10], protein [11,12], glucose [13], etc. The package of the ISFET which protects the drain/source metals of the device from being corroded by the solution plays an important role
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