AlGaN/GaN high-electron-mobility transistor pH sensor with extended gate platform

Abstract

In this paper, we fabricated an AlGaN/GaN high electron mobility transistor (HEMT) pH sensor with an extended-gate (EG). As the carrier mobility of the transducer that is used as the biosensor is increased, the electrical signal conversion efficiency of the biomaterials is improved. Therefore, the HEMT is a more suitable transducer platform than the conventional silicon-based transistor. The fabricated AlGaN/GaN device showed an electron density of 9.0 × 1012 cm-2, and an electron mobility of 1,990 cm2/V-s. In order to reduce the gate leakage current, which is a drawback of conventional HEMT devices, we deposited a 3-nm thick Al2O3 layer as a top-gate oxide by the atomic layer deposition (ALD) method; the fabricated HEMT has a metal–insulator semiconductor (MIS) structure. In addition, we used the EG to implement the disposable biosensor. Although the EG (a sensing membrane) is contaminated and destroyed, the HEMT (a transducer) can be reused. We evaluated the pH sensing characteristics using a pH sensor, which was implemented by connecting the HEMT and EG. The EG HEMT pH sensor showed a sensitivity of 57.6 mV/pH, which is close to the Nernst limit (approximately 59 mV/pH), and a linearity of 98.93%. To verify the stability and reliability of the implemented EG HEMT pH sensor, we measured the real-time response. The EG HEMT pH sensor has an error of only 2.39% of the signal. Therefore, we expect that the EG-based AlGaN/GaN HEMT pH sensor will be a suitable next-generation biosensor platform for a high electrical signal change efficiency of biomaterials, disposable, and point-of-care systems.

Status and Prospects of Heterojunction-Based HEMT for Next-Generation Biosensors

“…Extended-gate HEMT has also been proposed as a pH detection sensor. Pyo et al demonstrated a pH EG-HEMT sensor by connecting the sensing structure, fabricated with tin dioxide (SnO 2 ), to an HEMT device [ 133 ]. It is noteworthy to mention that the HEMT was constructed using metal-insulator semiconductor (MIS) structure to overcome the unstable gate leakage of conventional metal-semiconductor (MS) HEMT structures.…”

Deep-ultraviolet integrated photonic and optoelectronic devices: A prospect of the hybridization of group III–nitrides, III–oxides, and two-dimensional materials

“…The heterogeneous integration of various forms of inorganic materials (which encompasses growing numbers of material types) into one electronic system is based on group III-nitride compound semiconductors [17][18][19][20][21][22][23][24][25][26][27][28] . Examples include the following: on-chip frequency upconversion [29] , nanomechanical optical detection [30,31] , solid-state neutron detection [32][33][34] , piezoelectric resonators and electrical and harmonic generators [35][36][37][38][39][40] , strain-gated transistors (SGTs) [41] , multiple-valued logic (MVL) circuits [42] , single-photon emission [43][44][45] , water splitting [46][47][48][49][50][51] , solar-blind photodetection [52] , pressure [53] , gas [54] , pH [55] , sensors, white light generation from light-emitting diodes (LEDs) [56][57][58] and from laser diodes (LDs) [59] , metal-oxidesemiconductor field-effect transistors (MOSFETs) [60]…”

Investigation of Sc2O3 Based All-Solid-State EIS Structure for AlGaN/GaN HEMT pH Sensor

“…The last step of the fabrication is gold wire (with diameter of 25 pm) bonding between two Au/Ti contacts located in two different reservoirs. Instead of the usual deposition of metal on the backside of the semiconductor substrate, a large capacitive virtual ground contact (Au/Ti) around the MIS gate contact and EIS reservoir [19] has been used. The ground contact was made large enough so that its capacitance is much higher than the one of the MIS and EIS capacitors to study.…”