Editors' Choice—On the Radiation Tolerance of AlGaN/GaN HEMTs

Abstract

The radiation tolerance of AlGaN/GaN high electron mobility transistors (HEMTs) fabricated on high quality, low threading dislocation density (TDD) ammonothermal GaN and hydride vapor phase epitaxy GaN substrates was studied and compared to the radiation response of devices on SiC substrates where the TDD is 10 4 times higher. Hall and transport measurements were performed as a function of 2 MeV proton fluence. The threading dislocation density had no effect on the radiation response. Comparing the results with published data reveals that almost all irradiated GaN-based HEMTs respond to radiation damage similarly regardless of differences in initial film quality, device structure, aluminum mole fraction, etc. AlGaAs/GaAs HEMTs are also shown to behave similarly but are around ten times more sensitive to radiation damage than GaN-based HEMTs. Known values of the displacement energy thresholds in GaN and GaAs are used to calculate that 36% fewer defects are created in GaN than in GaAs, which is too small to cause a 1000% difference in radiation sensitivity between GaN-and GaAs-based HEMTs. An alternative explanation is proposed in which the piezoelectric field at the AlGaN/GaN interface causes scattered carriers to be reinjected into the 2DEG channel, thereby mitigating some of the harmful radiation effects.

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

“…These properties make III-V nitride an attractive electronic material for high-temperature and harsh-radiation environments. [1][2][3][4] Furthermore, gallium nitride (GaN) FETs have several advantages over traditional silicon FETs, including smaller size, lower weight, and higher efficiency.…”

Effect of Surface Passivation and Substrate on Proton Irradiated AlGaN/GaN HEMT Transport Properties

“…These effects may be a result of the reduced threading dislocation density in homoepitaxially grown GaN. 2,3,11 After irradiation, the mobility and resistivity drop to similar values to Sample A since impurity scattering is now the dominate factor. The sheet density (Figure 3h) drops at lower fluences due to increased electron donor traps in the AlGaN layer; however, these traps are deeper since they are still frozen out at room temperature.…”

“…In particular, it has been shown that switching to a AlN-passivated layer improves transistor performance, 10 while switching to a GaN substrate reduces threading dislocation densities by 4 orders of magnitude. 2,3,11 Previous experimental and theoretical studies have determined temperature dependent AlGaN/GaN Hall effect measurements result in the mobility being limited by piezoelectric scattering and ionized impurity scattering at low temperatures and phonon scattering at high temperatures. [12][13][14] However, the effect of radiation on these properties has not be examined.…”

Impact of 2 MeV Proton Irradiation on the Large-Signal Performance of Ka-Band GaN HEMTs

“…4 In addition, mobility has been shown to be degraded due to scattering induced by roughening of the AlGaN/GaN interface. 12 The reduction in gate leakage has also been previously observed and has been attributed to radiation-induced void formation as a result of Kirkendall diffusion in the Ni/Au gate metallization.…”

“…The fluence schedule ranged from 1 × 10 12 to 6 × 10 14 H + /cm 2 , and was designed to induce clear degradation in the DC characteristics based on prior work on GaN HEMTs. 4 To place this work into perspective, the maximum fluence tested represents >6,000 years in geostationary orbit. 8 Before and after irradiation, DC I-V sweeps were taken on all devices using a Keithley 4200 SCS.…”