Role of Gate Oxide in AlGaN/GaN High-Electron-Mobility Transistor pH Sensors

Abstract

We report on a comparison of different gate oxides for AlGaN/GaN highelectron-mobility transistor (HEMT) pH sensors. The HEMTs show a linear increase in drain-source current as the pH of the electrolyte solutions introduced to the gate region is decreased. Three different gate oxides were examined, namely the native oxide on the AlGaN surface, a UV-ozone-induced oxide and an Sc 2 O 3 gate deposited by molecular beam epitaxy. The Sc 2 O 3 produced superior results in terms of resolution in measuring small changes in pH. The devices with Sc 2 O 3 in the gate region exhibited a linear change in current between pH 3 and 10 of 37 lA/pH with a resolution of <0.1 pH over the entire pH range. In contrast, the native oxide devices showed a larger change in current, $70 lA/pH, but with a degraded resolution of $0.4 pH. Results for the UV-ozone oxide were intermediate in resolution, 0.2 pH. These HEMTs have promise for detecting pH changes in biological samples and can be readily integrated into a standard package for wireless data transmission.

Synchrotron-based XPS studies of AlGaN and GaN surface chemistry and its relationship to ion sensor behaviour

“…For pH values above neutral, both GaN and AlGaN show decreasing I ds with increasing pH [18,20,31]. This is consistent with our results for both RTA oxidised GaN and RTA oxidised AlGaN surfaces which showed that exposure to NaOH/NaCl results in OH − formation (seen in Fig.…”

Wireless Detection System for Glucose and pH Sensing in Exhaled Breath Condensate Using AlGaN/GaN High Electron Mobility Transistors

“…The epi-layers were grown by Metal-Organic Chemical Vapor Deposition on Si substrates. The sheet carrier concentration was cm and the mobility was 980 cm /V-s at 300 K. For the pH sensing, 100 Å Sc O was deposited as a gate dielectric through a contact window of SiNx layer [22], [23]. Fig.…”

On a GaN-based ion sensitive field-effect transistor (ISFET) with a hydrogen peroxide surface treatment

“…on GaN-based ISFETs were investigated and demonstrated [12,14,15]. A variety of methods are frequently to deposit metal-oxide membrane layers, such as sputtering, chemical vapor deposition, atomic layer deposition, and chemical wetness technique.…”

“…A variety of methods are frequently to deposit metal-oxide membrane layers, such as sputtering, chemical vapor deposition, atomic layer deposition, and chemical wetness technique. [13][14][15][16]. However, the former three methods belonging to high-energy processes might damage the chemical composition and induce surface defects, which would cause the long-term instability and poor reliability of an ISFET [17].…”