Enhancing the electron mobility in Si-doped (010) β-Ga ₂ O ₃ films with low-temperature buffer layers

Journal Article · Wed Feb 01 00:00:00 EST 2023 · APL Materials

DOI:https://doi.org/10.1063/5.0137666· OSTI ID:1958332

Bhattacharyya, Arkka  ^[1]; Peterson, Carl  ^[1]; Itoh, Takeki  ^[1]; Roy, Saurav  ^[1]; Cooke, Jacqueline  ^[2]; Rebollo, Steve  ^[1]; Ranga, Praneeth  ^[2]; Sensale-Rodriguez, Berardi  ^[2]; Krishnamoorthy, Sriram  ^[1]

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1. Materials Department, University of California Santa Barbara, Santa Barbara, California 93106, USA
2. Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, Utah 84112, USA

We demonstrate a new substrate cleaning and buffer growth scheme in β-Ga ₂ O ₃ epitaxial thin films using metal–organic vapor phase epitaxy (MOVPE). For the channel structure, a low-temperature (LT, 600 °C) un-doped Ga ₂ O ₃ buffer was grown, followed by a transition layer to a high-temperature (HT, 810 °C) Si-doped Ga ₂ O ₃ channel layers without growth interruption. The (010) Ga ₂ O ₃ Fe-doped substrate cleaning uses solvent cleaning, followed by additional hydrofluoric acid (49% in water) treatment for 30 min before the epilayer growth. This step is shown to compensate the parasitic Si channel at the epilayer–substrate interface that originates from the substrate polishing process or contamination from the ambient. From secondary ion mass spectroscopy (SIMS) analysis, the Si peak atomic density at the substrate interface is found to be several times lower than the Fe atomic density in the substrate—indicating full compensation. The elimination of the parasitic electron channel at the epi–substrate interface was also verified by electrical (capacitance–voltage profiling) measurements. In the LT-grown (600 °C) buffer layers, it is seen that the Fe forward decay tail from the substrate is very sharp, with a decay rate of ∼9 nm/dec. X-ray off-axis rocking curve ω-scans show very narrow full width at half maximum (FWHM) values, similar to the as-received substrates. These channels show record high electron mobility in the range of 196–85 cm ² /V⋅s in unintentionally doped and Si-doped films in the doping range of 2 × 10 ¹⁶ –1 × 10 ²⁰  cm ⁻³ . Si delta-doped channels were also grown utilizing this substrate cleaning and the hybrid LT buffers. Record high electron Hall mobility of 110 cm ² /V⋅s was measured for sheet charge density of 9.2 × 10 ¹²  cm ⁻² . This substrate cleaning, combined with the LT buffer scheme, shows the potential of designing Si-doped β-Ga ₂ O ₃ channels with exceptional transport properties for high-performance Ga ₂ O ₃ -based electron devices.

• Sponsoring Organization: USDOE
• OSTI ID: 1958332
• Journal Information: APL Materials, Journal Name: APL Materials Vol. 11 Journal Issue: 2; ISSN 2166-532X
• Publisher: American Institute of Physics
• Country of Publication: United States
• Language: English