Abstract Body: β-Ga2O3 is an emerging ultra-wide bandgap (UWBG) semiconductor that holds promise to enable advances in power, RF and opto-electronic devices. With the introduction of β-(Al,Ga)2O3, UWBG heterostructures are possible that increase the range of viable devices. In fact, two-dimensional electron gases (2DEG) in modulation-doped β-(Al,Ga)2O3/Ga2O3heterojunctions [1, 2] have already been reported. However, while there are numerous studies on defect spectroscopies and electrical properties of β-Ga2O3, comparatively little information on electrically active defects and their impact on material properties in β-(Al,Ga)2O3 is available. An understanding of traps in β-(Al,Ga)2O3 will be important to identify and mitigate sources for device degradation, as well as to optimize epitaxial growth. Presented here are deep level transient and optical spectroscopy (DLTS/DLOS) results obtained from β-(Al0.1Ga0.9)2O3 epitaxial layers grown by metal organic chemical vapor deposition (MOCVD). These are discussed in the context of our prior β-Ga2O3 results, to provide a baseline from which trends and conclusions can be provided. MOCVD was used to grow b-(Al0.1Ga0.9)2O3 layers in an Agnitron Agilis R&D system, using TEGa, TMAl and O2 precursors on β-Ga2O3 (010) Sn-doped EFG-grown substrates with a growth temperature of 880 °C. To enable useful comparisons with our β-Ga2O3 results, an Al cation mole fraction of 0.10 was targeted for our initial studies, which should yield a bandgap of approximately 5.0 eV. Ni Schottky diodes were fabricated on the sample using conventional photolithography methods. Capacitance-voltage, current-voltage and internal photoemission measurements (IPE) revealed the Schottky diodes were suitable for defect spectroscopy measurements and characterize the Ni/b-(Al0.1Ga0.9)2O3 Schottky properties themselves. Comparisons are made to previously characterized Schottky diodes fabricated on a β-Ga2O3 epitaxial film grown by MOCVD in the same reactor under the same growth conditions [3]. The net doping concentration in the initial layers under study was measured by CV to be 1.8 x 1018 cm-3. Good Schottky behavior was observed, even at this high doping value, with strong rectification, ideality factor of ~1.5, and IPE-determined Schottky barrier heights of ~1.4 V. Preliminary deep level defect characterization using admittance spectroscopy (AS) along with DLTS and DLOS revealed the presence of five trap states within the b-(Al0.1Ga0.9)2O3 bandgap. A state with an activation energy of ~EC-0.2 eV as observed by AS; three trap levels were revealed by DLTS with approximate trap energies of ~EC-0.3 eV, ~EC-0.4 eV and EC-0.8 eV; and two trap levels were observed in the steady-state photo-capacitance (SSPC) spectra having onset energies of ~EC-2.0 eV and ~EC-4.6 eV. Overall, a similar energy distribution of trap states is observed compared with MOCVD grown b-Ga2O3 is suggestive of similar physical sources of traps between these the two materials, accounting for the small bandgap differences. A notable difference is the EC-0.8 eV trap, which is absent in the MOCVD b-Ga2O3, but matches the signature in b-Ga2O3 grown by other techniques suggesting it may be related to Fe [4]. Much more work is needed to confirm the meaning of these observations, which is ongoing. However, total trap concentrations are markedly different, being ~ 100x larger in the b-(Al0.1Ga0.9)2O3 epitaxial films, which is indicative of the very early stage of β-(Al,Ga)2O3 epitaxial growth development. Complete discussion of the nature of the traps seen in b-(Al0.1Ga0.9)2O3 and an expanded range of alloy compositions and growth conditions will be presented, including further comparisons to prior data obtained from high quality b-Ga2O3[3]. [1] N. Kalarickal, et al, J. Appl. Phys. 127, 215706 (2020) [2] Y. Zhang, et al, Appl. Phys. Lett. 112, 233503 (2018) [3] H. Ghadi, et al, Appl. Phys. Lett. 117, 172106 (2020) [4] J. F. McGlone, et al, Electron Dev. Lett. 39, 1042 (2018)

Quantitative Defect Characterization of MOCVD-Grown β-(Al,Ga)2O3 and Comparison with β-Ga2O3

Ohio State Univerisity

gallium oxide

aluminum gallium oxide

deep level transient spectroscopy

orientation-dependent band offsets

β-(alxga1−x)2o3 thin film

β-ga2o3

valance band offset

conduction band offset

buffer leakage

dispersion

Bhuiyan A F M Anhar Uddin

1

3

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