Real-time X-ray response of AlGaN/GaN-HEMT devices

We present the real-time X-ray irradiation response of charge and pH sensitive solution gate AlGaN/GaN high electron mobility transistors (HEMTs). At the interface of the two materials a fixed space charge appears due to the difference in polarisation of the materials and a two-dimensional electron gas (2DEG) is produced. The electrical properties and therefore the conductivity of the system highly depend on the chip surface potential. We could demonstrate that the devices are stable and show reproducible behavior under and following X-ray radiation at different energies, including a linear integrated response with dose into the micro-gray range. Titration measurements of devices in solution reveal that the linear pH response and sensitivity are not only retained under X-ray irradiation, but an irradiation response could also be measured. The active areas of the sensors are in the size of about 1 mm2, which makes them an ideal candidate for dose determination in radiology applications. The devices are bio-compatible and can be simultaneously operated in aggressive fluids and under hard radiation. The development of this sensor device, which provides the possibility of online radiation dosimetry acquisition during biosensing applications, has a huge potential in radiation biophysics.