Cathodoluminescence Studies of Gamma-Irradiation Effects on AlGaN/GaN High Electron Mobility Transistors (HEMTs)

The effects of 60Co gamma-irradiation on AlGaN/GaN High Electron Mobility Transistors (HEMTs) were studied by means of temperature dependent Cathodoluminescence (CL). The CL spectra were examined for several devices with radiation exposures of gamma-ray doses up to 1000 Gy, and for temperature ranging from 25°C to 125°C. Gamma-irradiation causes the CL intensity of HEMTs to decrease by creating defects that act as non-radiative recombination centers. The activation energy was observed to decrease as dosage was incremented to 200 Gy. The decrease in activation energy is related to Compton electron induced increase in carrier lifetime. However for doses above 200 Gy, the activation energy increases as the dose increases. This behavior could be explained by the formation of large electrically active defect complexes through the addition of new radiation defects to the defects formed at low doses.