Crystal orientation dependence of deep level spectra in proton irradiated bulk β-Ga2O3

The effects of 20MeV proton irradiation with fluences of 5x10(14) and 10(15)p/cm(2) on electrical properties of lightly Sn doped n-type (net donor concentration 3x10(17)cm(-3)) bulk beta-Ga2O3 samples with (010) and (-201) orientation were studied. Proton irradiation decreases the net donor density with a removal rate close to 200cm(-1) for both orientations and similar to the electron removal rates in lightly Si doped beta-Ga2O3 epilayers. The main deep electron traps introduced in the beta-Ga2O3 crystals of both orientations are near E-c-0.45eV, while in Si doped films, the dominant centers were the so-called E2* (E-c-0.75eV) and E3 (E-c-0.1eV) traps. Deep acceptor spectra in our bulk -Ga2O3(Sn) crystals were dominated by the well-known centers with an optical ionization energy of near 2.3eV, often attributed to split Ga vacancies. These deep acceptors are present in a higher concentration and are introduced by protons at a higher rate for the (010) orientation. Another important difference between the two orientations is the introduction in the surface region (similar to 0.1 mu m from the surface) of the (010) of a very high density of deep acceptors with a level near E-c-0.27eV, not observed in high densities in the (-201) orientation or in Si doped epitaxial layers. The presence of these traps gives rise to a very pronounced hysteresis in the low temperature forward current-voltage characteristics of the (010) samples. These results are yet another indication of a significant impact of the orientation of the beta-Ga2O3 crystals on their properties, in this case, after proton irradiation. Published under an exclusive license by AIP Publishing.

Automated summary

The study investigates the effects of 20MeV proton irradiation on the electrical properties of lightly Sn doped beta-Ga2O3 crystals, revealing a decrease in net donor density, introduction of deep electron traps, and deep acceptors. The results suggest a significant impact of crystalline orientation on the properties after proton irradiation.