The Leakage Mechanism of the Package of the AlGaN/GaN Liquid Sensor

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.

A Review on Gallium Nitride for Liquid Sensors: Fabrications to Applications

“…29 In addition, the electrical and mechanical properties of GaN make it an appropriate material for sensing applications. The physical properties incorporate a wide direct bandgap (3.39), a relative density of 6.15 g/cm 3 , and a melting point of 2500 °C, whereas the electrical properties consist of high electron mobility near 2000 cm 2 /(V• s) at 300 K. 30 For applications like liquid sensors (LSs) and WS, DOS and the band diagram are important factors since they provide critical information about the properties of the material. The band diagram exposes the presence of energy levels within the bandgap, such as surface states, which can influence the interaction between GaN and water, while the DOS gives information about the distribution of energy states available for charge carriers in GaN, which is significant for LSs that depend on electrical conductivity changes.…”

“…Moreover, its unique material properties, including chemical stability, high electron concentration, and high mobility in the heterojunction two-dimensional electron gas (2DEG) channel, enable them to achieve remarkable sensitivity. 3 The III−V material is usually grown using Metal Oxide Chemical Vapor Deposition (MOCVD) 4 or Molecular Beam Epitaxy (MBE). 5 In the past decade, exceptional advancements have been made in the field of wide-bandgap (WBG) semiconductors, such as diamonds, silicon carbide (SiC), GaN, or III-nitrides.…”

“…GaN material possesses good thermal conductivity, enabling GaN-based devices to function effectively under high-temperature and harsh environmental conditions. Moreover, its unique material properties, including chemical stability, high electron concentration, and high mobility in the heterojunction two-dimensional electron gas (2DEG) channel, enable them to achieve remarkable sensitivity . The III–V material is usually grown using Metal Oxide Chemical Vapor Deposition (MOCVD) or Molecular Beam Epitaxy (MBE) …”

Flexible Electrode by Hydrographic Printing for Surface Electromyography Monitoring

“…Dry flexible electrode is a promising alternative as they can attach to skin with intimate attachment, less motion artifact and no skin reaction [18]. While most dry flexible electrodes are typically based on polymer [19] (PDMS [20], PI [21]), metal (Au [22], AgNP [23]), carbon [24,25] and liquid metal (AlGaN/GaN [26], EGaIn [27][28][29]). Previous works also typically proved that rigid metal materials (Au [30], Cu [31]) with serpentine and bridge structure [32] could better tolerate mechanical deformations such as stretching, compressing and twisting.…”