Iron and intrinsic deep level states in Ga2O3

Abstract

Using a combination of deep level transient spectroscopy, secondary ion mass spectrometry, proton irradiation, and hybrid functional calculations, we identify two similar deep levels that are associated with Fe impurities and intrinsic defects in bulk crystals and molecular beam epitaxy and hydride vapor phase epitaxi-grown epilayers of β-Ga2O3. First, our results indicate that FeGa, and not an intrinsic defect, acts as the deep acceptor responsible for the often dominating E2 level at ∼0.78 eV below the conduction band minimum. Second, by provoking additional intrinsic defect generation via proton irradiation, we identified the emergence of a new level, labeled as E2*, having the ionization energy very close to that of E2, but exhibiting an order of magnitude larger capture cross section. Importantly, the properties of E2* are found to be consistent with its intrinsic origin. As such, contradictory opinions of a long standing literature debate on either extrinsic or intrinsic origin of the deep acceptor in question converge accounting for possible contributions from E2 and E2* in different experimental conditions.

Deep level defects in Ge-doped (010) β-Ga2O3 layers grown by plasma-assisted molecular beam epitaxy

“…The main peak is now clearly resolved, and the results are plotted alongside the conventional DLTS trap data on the Arrhenius plot, giving an energy level of E C À 0.98 6 0:06 eV with an electron capture cross section of (0.1-9)Â10 À14 cm 2 and a trap concentration of $1.6 Â 10 15 cm À3 . As discussed later, this level is close to the one previously reported in both EFG 8,20,21 and CZ 7 UID (n-type, Si background) substrate materials. 7,8 The appearance of other smaller peaks in the isothermal transient analysis could suggest the presence of even deeper traps that are not resolvable.…”

“…[21][22][23] These works provide excellent points of comparison for the DLTSdetected states within the upper region of the bandgap reported here for the Ge-doped PAMBE-grown material, where the role of dopant species is also a point of consideration given the lack of data available to date. [21][22][23] From extensive past efforts on GaN, both very deep and shallower defect states have been known to have a major impact on device performance parameters such as threshold voltage, carrier mobility, on-resistance, and DC-to-RF dispersion through trapping effects. [24][25][26] Thus, the knowledge about the presence and the properties of deep level defect states throughout the b-Ga 2 O 3 bandgap of epitaxial materials is likely to be critical for the reliable and high-performance future gallium oxide transistors.…”

“…7,8 DLTS studies have also been performed on (010), (001), and (100) b-Ga 2 O 3 homoepitaxial layers grown by MBE, HVPE, and MOVPE. [21][22][23] DLOS results have only been reported for UID EFG material for (010) and (-201) orientations. 8,11 Given TABLE I.…”

“…8 7 and EFG-grown (-201). 20,21 Additionally, there is a growing body of DLTS work being performed on various UID and Si-doped (010), (001) and (100) oriented b-Ga 2 O 3 homoepitaxy materials grown by MBE, hydride vapor phase epitaxy (HVPE), and metalorganic vapor phase epitaxy (MOVPE). [21][22][23] These works provide excellent points of comparison for the DLTSdetected states within the upper region of the bandgap reported here for the Ge-doped PAMBE-grown material, where the role of dopant species is also a point of consideration given the lack of data available to date.…”

“…20,21 Additionally, there is a growing body of DLTS work being performed on various UID and Si-doped (010), (001) and (100) oriented b-Ga 2 O 3 homoepitaxy materials grown by MBE, hydride vapor phase epitaxy (HVPE), and metalorganic vapor phase epitaxy (MOVPE). [21][22][23] These works provide excellent points of comparison for the DLTSdetected states within the upper region of the bandgap reported here for the Ge-doped PAMBE-grown material, where the role of dopant species is also a point of consideration given the lack of data available to date. [21][22][23] From extensive past efforts on GaN, both very deep and shallower defect states have been known to have a major impact on device performance parameters such as threshold voltage, carrier mobility, on-resistance, and DC-to-RF dispersion through trapping effects.…”