Radiation Damage in the Ultra-Wide Bandgap Semiconductor Ga₂O₃

Abstract

Ga2O3 is expected to show similar radiation resistance to that of GaN and SiC. This is not enough to explain the orders of magnitude difference in the relative resistance to radiation damage of these materials compared to GaAs or why dynamic annealing of defects is much more effective in Ga2O3. Octahedral gallium monovacancies are the main defects produced under most radiation conditions because of the larger cross-section for interaction compared to oxygen vacancies. Proton irradiation introduces two main paramagnetic defects in Ga2O3, which are stable at room temperature. Charge carrier removal can be explained by Fermi-level pinning far from the conduction band minimum due to gallium interstitials, vacancies, and antisites. With few experimental or simulation studies on single event effects in Ga2O3 , it is apparent that while other wide bandgap semiconductors like SiC and GaN are robust against displacement damage and total ionizing dose, they display significant vulnerability to single event effects at high linear energy transfer and at much lower biases than expected. We have analyzed the transient response of β-Ga2O3 rectifiers to heavy-ion strikes via TCAD simulations. Using field metal rings improves the breakdown voltage and biasing those rings can help control the breakdown voltage.

15 MeV proton damage in NiO/β-Ga2O3vertical rectifiers

“…Since the NIEL is approximately constant over the drift layer thickness, this provides a reasonable estimate the carrier removal rate. The values obtained here for the NiO/Ga 2 O 3 , 1200 for 10 13 cm −2 and 190 cm −1 for 10 14 cm −2 are consistent with values reported for proton irradiation at similar energies/fluences but in Schottky diode structures that did not include the NiO [26,27]. This indicates that in contrast to gamma irradiation [29], the heterojunction rectifiers do not show any significant differences with the presence of the NiO for proton damage.…”

“…The carrier removal rate per ion was then obtained from the change in carrier density divided by the fluence and is included in the compilation plot of figure 8, which shows the published values for different polymorphs of Ga 2 O 3 irradiated with different forms of radiation [26,27]. Since the NIEL is approximately constant over the drift layer thickness, this provides a reasonable estimate the carrier removal rate.…”

“…While the device performance is promising in terms of dc and switching applications [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26], little is known about the effects of radiation on these heterojunctions. While the Ga 2 O 3 is known to be relatively resistant to total dose damage [27,28], large reversible changes in current-voltage characteristics of the heterojunctions have been observed after Co-60 gamma ray exposure which appears to be due to conductivity changes in the NiO [29]. Other low dose ion irradiated oxides have also shown enhanced conductivity which in some cases has been linked to irradiation/illumination assisted desorption of oxygen containing species from the oxide surface [30][31][32][33].…”

Comparison of 10 MeV Neutron Irradiation Effects on NiO/Ga2O3 Heterojunction Rectifiers and Ni/Au/Ga2O3 Schottky Rectifiers

“…These are expected to be similar since the depletion in the both the p-n heterojunctions and the Schottky rectifier will be in the n-Ga 2 O 3 . As tabulated in Table I, the carrier concentration is slightly reduced after neutron irradiation, with an approximate carrier removal rate, R C , defined by 44,45 where Φ is the neutron fluence, n s0 is initial carrier concentration, and n s is the irradiated carrier concentration. The R C value was ∼45 cm −1 , which is broadly consistent with reported values for neutrons with similar or lower energies, given the large uncertainties in some cases of this parameter.…”

“…38 While neutrons are the least damaging from this regard, their ubiquity in the environment means there is a need to understand their effects on Ga 2 O 3 -based devices. [41][42][43][44][45] In this paper, we report a comparison of 10 MeV neutron irradiation of NiO/Ga 2 O 3 heterojunction rectifiers with conventional Schottky Ga 2 O 3 rectifiers. We find no significant difference in the response of the two types of rectifiers to neutron irradiation, and a high degree of robustness against neutron damage in both cases.…”