Cumulative dose γ-irradiation effects on material properties of AlGaN/GaN hetero-structures and electrical properties of HEMT devices

Abstract

The effects of γ-ray irradiation on AlGaN/GaN epitaxial layers and on high electron mobility transistor (HEMT) devices have been systematically investigated. The layer structure and HEMT device has been irradiated cumulatively with γ-ray dose of the order of 16 kGy. The x-ray diffraction (XRD) analysis of irradiated sample shows a lowering in full width at half maximum (FWHM) values along (102) and (002) planes in comparison to the pristine sample due to partial annealing effect. A decrease in the in-plane biaxial stress from 1.20 GPa to 0.75 GPa has been observed. Raman spectrum analysis also corroborates the reduction in stress post γ-ray irradiation. Edge dislocation density is reduced from 2.7×10 8 cm −2 to 1.75×10 8 cm −2 whereas the screw dislocation density remains almost unaffected. Further, Hall measurement shows an improvement in the mobility from 1580 cm 2 V −1 s −1 to 2070 cm 2 V −1 s −1 with reduction in sheet resistance. This improvement in mobility is attributed due to the decrease in surface roughness as confirmed by atomic force microscopy (AFM) characterization and also due to re-arrangement of the local defect centers as confirmed by cathodoluminescence (CL) imaging analysis. Finally, an increase in drain current from 99.5 mA mm −1 to 121.2 mA mm −1 with reduction in leakage current has been observed in case of HEMT device due to the improvement found in various material parameters.

Effects of γ-Ray Irradiation on AlGaN/GaN Heterostructures and High Electron Mobility Transistor Devices

“…The introduced defects modified the native defect structure and achieved a uniform distribution. 18 In our previous studies x-ray photoelectron spectroscopy, 22 x-ray diffraction (XRD), and CL imaging 23 results have shown that c-irradiation has partial annealing effects. These effects cause the reduction of dangling bonds at the surface as a result of oxidation and structural-chemical ordering at the interface.…”

“…In our previous study involving the use of a similar c-ray dose range to that used in this study, we performed photoluminescence and XRD analysis and observed a reduction in the number of optically active defects as well as a simultaneous redistribution and annealing of defects or traps. 23 The increase in I D and marginal decrease in I G were saturated after or at the third irradiation dose (16 kGy). This trend of saturation in the parameters was similar to that observed in the material parameters.…”

“…[26][27][28] Several studies have reported that improvements occur in the interface and material properties of GaN after c-ray irradiation as a result of trap or defect annealing or redistribution. 10,18,19,23 Because of the partial annealing of traps or defects, the degree of trapassisted tunneling decreased and I G reduced after irradiation. In our previous study involving the use of a similar c-ray dose range to that used in this study, we performed photoluminescence and XRD analysis and observed a reduction in the number of optically active defects as well as a simultaneous redistribution and annealing of defects or traps.…”

Interplay Between γ–Ray Irradiation and 3DEG for Dosimeter Applications

“…In this regard, several attempts have been made to assess the reliability of GaN HEMTs in the presence of ionizing radiations for specific applications in nuclear reactors and space. Several studies have also reported the sensitivity of GaN HEMT devices towards the ionizing X -Rays [26][27][28] and γ -Rays [28][29][30][31][32]. The impact of γ -Rays irradiation on reported HEMT architectures is compiled in Table I [28][29][30][31][32].…”

“…Several studies have also reported the sensitivity of GaN HEMT devices towards the ionizing X -Rays [26][27][28] and γ -Rays [28][29][30][31][32]. The impact of γ -Rays irradiation on reported HEMT architectures is compiled in Table I [28][29][30][31][32].…”