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

Abstract

The effects of 20 MeV proton irradiation with fluences of 5 × 1014 and 1015 p/cm2 on electrical properties of lightly Sn doped n-type (net donor concentration 3 × 1017 cm−3) bulk β-Ga2O3 samples with (010) and (−201) orientation were studied. Proton irradiation decreases the net donor density with a removal rate close to 200 cm−1 for both orientations and similar to the electron removal rates in lightly Si doped β-Ga2O3 epilayers. The main deep electron traps introduced in the β-Ga2O3 crystals of both orientations are near Ec−0.45 eV, while in Si doped films, the dominant centers were the so-called E2* (Ec−0.75 eV) and E3 (Ec−0.1 eV) traps. Deep acceptor spectra in our bulk –Ga2O3(Sn) crystals were dominated by the well-known centers with an optical ionization energy of near 2.3 eV, 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 (∼0.1 μm from the surface) of the (010) of a very high density of deep acceptors with a level near Ec−0.27 eV, 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 β-Ga2O3 crystals on their properties, in this case, after proton irradiation.

Vertical van der Waals heterojunction diodes comprising 2D semiconductors on 3D β-Ga2O3

“…Hydrogen for instance has been shown to form complexes with split Ga vacancies most effectively in the (−201) orientation, yielding higher diffusion coefficients in the (010) direction than in the (−201). 47 Previous studies have reported a β-Ga 2 O 3 thermal conductivity approximately three times larger along the (010) direction than along the (100). 13 Asymmetric phonon modes were also suggested as the cause of significant anisotropic carrier scattering and variations in electron mobility in β-Ga 2 O 3 FETs.…”

Radiation Damage in the Ultra-Wide Bandgap Semiconductor Ga2O3

“…Total dose damage.-Since Ga 2 O 3 devices and more generally all wide bandgap semiconductor devices normally use metal gates, Total Ionizing Dose (TID) effects are not as important as they are in Si technology, 40,[66][67][68][69][70] which is based on MOS-gate devices. The relations between charge (e) and electric field, E (Poisson's equation) and the transport (drift/diffusion) equations depend on carrier mobility (μ e,p ) and density (n,p), i.e.,…”

“…While significant work has been done for radiation effects in GaN [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]59 and SiC, [43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][60][61][62][63][64][65] the understanding of carrier removal rates, defect levels and annealing regimes for Ga 2 O 3 is on-going. [66][67][68][69][70][71][72] Spacecraft operating beyond Earth's magnetosphere are subject to space weather including the solar wind, a flux of radiation and charged particles that can degrade electronics. 73 These charged particles from the solar wind are also trapped inside the Earth's magnetosphere, forming the Van Allen radiation belts, which further expose transiting spacecraft to c...…”

Carrier removal rates in 1.1 MeV proton irradiated α-Ga2O3 (Sn)

“…Admittance spectra (AS) [31] at frequencies from 20 Hz to 2 MHz in the temperature range 100 K-450 K, and by deep level transient spectroscopy (DLTS) [20,31]. Details of the experimental setups can be found elsewhere [18,20,24,25,[32][33][34][35][36][37].…”

“…Proton irradiations were carried out at room temperature with energies 1.1 MeV, flux of 10 11 -10 12 cm −2 s −1 and fluences 10 13 , 10 14 , 10 15 or 10 16 cm −2 . The linear accelerator I-2 serving as a proton injector of a cyclotron with proton energy up to 10 GeV was used [32,[35][36][37]. The proton energy inside the accelerator was 24.6 MeV, the proton beam exited through a port into air, with the energy reduced to 22.5 MeV and further attenuated to the required energy using a set of calibrated metal foils (degraders) reducing the energy to 1.1 MeV.…”