High Electron Mobility Transistor Sensor Research Articles

Oxygen gas sensing at low temperature using indium zinc oxide-gated AlGaN/GaN high electron mobility transistors

Indium zinc oxide (IZO)-gated AlGaN/GaN high electron mobility transistors (HEMTs) were used to detect oxygen gas. Amorphous IZO films with high carrier concentration of 1021 cm−3 were deposited on the gate region of the HEMTs by cosputtering from ZnO and In2O3 targets. The changes in IZO gated-AlGaN/GaN HEMT drain current were used to monitor the presence of oxygen. The IZO gated AlGaN/GaN HEMT sensors were tested with O2 at room temperature, 50 °C, and 120 °C. There was no response to O2 at room temperature. At 50 °C, the sensors could sense O2 but gradually saturated. The sensor showed a strong response to the oxygen gas at 120 °C, which is a much lower temperature than with conventional oxide-based oxygen sensors that typically operate in the range of 400–700 °C. This enhanced oxygen sensing sensitivity was due to the amplification effect of the AlGaN/GaN HEMT. A preannealing step at 350 °C was also found to improve the sensitivity and response time of O2 sensing at 120 °C.

Detection of an endocrine disrupter biomarker, vitellogenin, in largemouth bass serum using AlGaN/GaN high electron mobility transistors

Endocrine disrupters are known to have negative effects on the environment and human health. Real time detection of vitellogenin, an endocrine disrupter biomarker, was demonstrated using AlGaN/GaN high electron mobility transistors (HEMTs). Anti-vitellogenin antibodies were chemically anchored to the gold-coated gate area of the HEMT and immobilized with thioglycolic acid. The potential difference that occurs from the vitellogenin antigen-antibody interaction-induced caused a drain current change in the HEMT. The HEMT sensor was tested for vitellogenin detection both in phosphate buffer saline and largemouth bass serum.

Aluminum Gallium Nitride (GaN)/GaN High Electron Mobility Transistor-Based Sensors for Glucose Detection in Exhaled Breath Condensate

Immobilized aluminum gallium nitride (AlGaN)/GaN high electron mobility transistors (HEMTs) have shown great potential in the areas of pH, chloride ion, and glucose detection in exhaled breath condensate (EBC). HEMT sensors can be integrated into a wireless data transmission system that allows for remote monitoring. This technology offers the possibility of using AlGaN/GaN HEMTs for extended investigations of airway pathology of detecting glucose in EBC without the need for clinical visits. HEMT structures, consisting of a 3-microm-thick undoped GaN buffer, 30-A-thick Al(0.3)Ga(0.7)N spacer, and 220-A-thick silicon-doped Al(0.3)Ga(0.7)N cap layer, were used for fabricating the HEMT sensors. The gate area of the pH, chloride ion, and glucose detection was immobilized with scandium oxide (Sc(2)O(3)), silver chloride (AgCl) thin film, and zinc oxide (ZnO) nanorods, respectively. The Sc(2)O(3)-gated sensor could detect the pH of solutions ranging from 3 to 10 with a resolution of approximately 0.1 pH. A chloride ion detection limit of 10(-8) M was achieved with a HEMT sensor immobilized with the AgCl thin film. The drain-source current of the ZnO nanorod-gated AlGaN/GaN HEMT sensor immobilized with glucose oxidase showed a rapid response of less than 5 seconds when the sensor was exposed to the target glucose in a buffer with a pH value of 7.4. The sensor could detect a wide range of concentrations from 0.5 nM to 125 microM. There is great promise for using HEMT-based sensors to enhance the detection sensitivity for glucose detection in EBC. Depending on the immobilized material, HEMT-based sensors can be used for sensing different materials. These electronic detection approaches with rapid response and good repeatability show potential for the investigation of airway pathology. The devices can also be integrated into a wireless data transmission system for remote monitoring applications. This sensor technology could use the exhaled breath condensate to measure the glucose concentration for diabetic applications.

Chloride ion detection by InN gated AlGaN∕GaN high electron mobility transistors

Real time chloride ion detection using InN gated AlGaN∕GaN high electron mobility transistors (HEMTs) was demonstrated. The InN thin film on the gate area of the HEMT provided fixed surface sites for reversible anion coordination. The drain current of the HEMT sensor exhibited increased a function of chloride ion concentration. The positive ions (Na+, Mg+2, and H+) in the chloride ion solutions showed no effect on the chloride ion concentration detection. The sensor was tested over a range of chloride ion concentrations from 100nMto100μM. The chloride ion HEMT sensors can be integrated with AlGaN∕GaN HEMT based pH and glucose sensors for exhaled breath condensate glucose monitoring technology. The HEMT based sensor can also be integrated into a wireless data transmission system for remote sensing applications.

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

Peltier element cooling of ungated AlGaN/GaN high electron mobility transistors (HEMTs) is shown to be an effective method for condensing exhaled breath, enabling the measurement of the pH and glucose of the exhaled breath condensate (EBC). By comparison with standard solutions, the current change measured in the HEMTs with EBC shows that the sensitivity of the glucose detection is lower than the glucose concentration in the EBC of healthy human subjects and the pH of the condensate from the exhaled breath is within the range of 7-8, typical of that for human blood. The HEMT sensors can be integrated into a wireless data transmission system that allows for remote monitoring. Details of the transmitter and receiver design for the transmission system are given. Our work demonstrates the possibility of using AlGaN/GaN HEMTs for extended investigations of airway pathology without the need for clinical visits.

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

Peltier element cooling is demonstrated to be an effective method for collecting exhaled breath condensate (EBC) on AlGaN/GaN High Electron Mobility Transistors (HEMT). The HEMT sensors have functionalized gate areas for glucose and pH measurement. The current change measured in the HEMTs with EBC shows that the sensitivity of the glucose detection is lower than the glucose concentration in the EBC of healthy person and the pH measurement range includes 7- 8, typical of that for human blood. The sensors can be integrated into a wireless data transmission system that allows remote monitoring. Details of the transmitter and receiver design for the transmission system are given. Our work demonstrates the possibility of using AlGaN/GaN HEMTs for extended investigations of airway pathology without the need for clinical visits.

Electrical detection of biomaterials using AlGaN/GaN high electron mobility transistors

Chemical sensors can be used to analyze a wide variety of environmental and biological gases and liquids and may need to be able to selectively detect a target analyte. Different methods, including gas chromatography, chemiluminescence, selected ion flow tube, and mass spectroscopy, have been used to measure biomarkers. These methods show variable results in terms of sensitivity for some applications and may not meet the requirements for a handheld biosensor. A promising sensing technology utilizes AlGaN/GaN high electron mobility transistors (HEMTs). HEMT structures have been developed for use in microwave power amplifiers due to their high two dimensional electron gas (2DEG) mobility and saturation velocity. The conducting 2DEG channel of AlGaN/GaN HEMTs is very close to the surface and extremely sensitive to adsorption of analytes. HEMT sensors can be used for detecting gases, ions, pH values, proteins, and DNA. In this paper we review recent progress on functionalizing the surface of HEMTs for specific detection of glucose, kidney marker injury molecules, prostate cancer, and other common substances of interest in the biomedical field.

Enzyme-based lactic acid detection using AlGaN∕GaN high electron mobility transistors with ZnO nanorods grown on the gate region

The detection of lactic acid with ZnO nanorod-gated AlGaN∕GaN high electron mobility transistors (HEMTs) was demonstrated. The array of ZnO nanorods provided a large effective surface area with a high surface-to-volume ratio and a favorable environment for the immobilization of lactate oxidase. The HEMT drain-source current showed a rapid response when various concentrations of lactic acid solutions were introduced to the gate area of the HEMT sensor. The HEMT could detect lactic acid concentrations from 167nM to 139μM. Our results show that portable, fast response, and wireless-based lactic acid detectors can be realized with AlGaN∕GaN HEMT based sensors.

Low Hg(II) ion concentration electrical detection with AlGaN/GaN high electron mobility transistors

Thioglycolic acid functionalized Au-gated AlGaN/GaN high electron mobility transistors (HEMTs) were used to detect mercury(II) ions. The drain current of the HEMT sensors monotonically increased with the mercury(II) ion concentration from 1.5 × 10−8 to 4 × 10−8 M. The drain current reached equilibrium around 15–20 s after the concentrated Hg ion solution added to the gate area of the HEMT sensors. The effectiveness of the thioglycolic acid functionalization was evaluated with a surface contact angle study. The results suggest that portable, fast response, and wireless-based heavy metal ion detectors can be realized with AlGaN/GaN HEMT-based sensors.

Potassium selective chemically modified field effect transistors based on AlGaN/GaN two-dimensional electron gas heterostructures

We investigate the use of the AlGaN/GaN high electron mobility transistor (HEMT) as a novel transducer for the development of ion-selective chemically modified HEMT sensors (ChemHEMTs). For this, polyvinyl chloride (PVC) membrane doped with ion-selective ionophores is deposited onto the area of the gate for the chemical recognition step, while the AlGaN/GaN HEMT is used as the transducer. In particular, the use of a valinocycin doped membrane with thickness of 50μm generates a sensor with excellent analytical characteristics for the monitoring of K+. The K+-ChemHEMT has sensitivity of 52.4mV/pK+in the linear range of 10−5 to 10−2M, while the detection limit is in the order of 3.1×10−6M. Also, the sensor shows selectivity similar to valinomycin-based ISEs, while the signal stability over time and the measurement to measurement reproducibility are very good.