Demonstration of high mobility and quantum transport in modulation-doped β-(AlxGa1-x)2O3/Ga2O3 heterostructures

Abstract

In this work, we demonstrate a high mobility two-dimensional electron gas (2DEG) formed at the β-(AlxGa1-x)2O3/Ga2O3 interface through modulation doping. Shubnikov-de Haas (SdH) oscillations were observed in the modulation-doped β-(AlxGa1-x)2O3/Ga2O3 structure, indicating a high-quality electron channel formed at the heterojunction interface. The formation of the 2DEG channel was further confirmed by the weak temperature dependence of the carrier density, and the peak low temperature mobility was found to be 2790 cm2/Vs, which is significantly higher than that achieved in bulk-doped Beta-phase Gallium Oxide (β-Ga2O3). The observed SdH oscillations allowed for the extraction of the electron effective mass in the (010) plane to be 0.313 ± 0.015 m0 and the quantum scattering time to be 0.33 ps at 3.5 K. The demonstrated modulation-doped β-(AlxGa1-x)2O3/Ga2O3 structure lays the foundation for future exploration of quantum physical phenomena and semiconductor device technologies based on the β-Ga2O3 material system.

Band Gap and Band Offset of Ga2O3 and (AlxGa<

“…It is available as large single crystals [6] suitable for high-quality epitaxial thin-film growth by metalorganic chemical vapor deposition (MOCVD) [7,8] and molecular beam epitaxy (MBE) [5,9]; It displays high breakdown electric field [1], and the Baliga figure of merit exceeds that of SiC and GaN [3]; It can be easily doped n-type, and band gap engineering can be accomplished by incorporating In and Al, adding great flexibility to device design. Modulation doping of (Al x Ga 1−x ) 2 O 3 /Ga 2 O 3 heterostructures can be used to separate the ionized donors in the (Al x Ga 1−x ) 2 O 3 layer from the conduction electrons in the Ga 2 O 3 layer [10][11][12][13], providing a boost to the electron mobility to about 500 cm 2 V −1 s −1 [10,14,15] by suppressing scattering from the ionized impurities. Simulated band diagrams and two-dimension electron gas (2DEG) profile of MODFETs based on (Al x Ga 1−x ) 2 O 3 /Ga 2 O 3 assumed that the discontinuity in the band offset appears solely on the conduction band [10].…”

“…These are listed in the Supplemental Material along the bowing parameters for the VBM and CBM separately [46]. The band offsets between (Al x Ga 1−x ) 2 O 3 and the parent compound Ga 2 O 3 are crucial parameters in the design of electronic devices that depend on carrier confinement or on the separation between carriers and ionized impurities such as in modulation-doped field-effect transistors (MODFETs) [10,15]. We calculated the band offset between two materials using the following procedure [47].…”

Identification and modulation of electronic band structures of single-phase β-(AlxGa1−x)2O3 alloys grown by laser molecular beam epitaxy

“…6 Furthermore, (Al x Ga 1Àx ) 2 O 3 /Ga 2 O 3 based high electron mobility transistors (HEMTs) with a twodimensional electron gas channel has been demonstrated through Si delta-modulation doping. [7][8][9] Whereas the channel mobility is still not far enough for high frequency applications, as it is limited by polar optical phonon scattering due to a higher electron effective mass of 2DEG. 7 The device performance of photodetectors and transistors are normally determined by the optical transition nature and intrinsic effective mass, and therefore, a deep understanding of the fundamental properties of (Al x Ga 1Àx ) 2 O 3 alloying materials is critical.…”

“…[7][8][9] Whereas the channel mobility is still not far enough for high frequency applications, as it is limited by polar optical phonon scattering due to a higher electron effective mass of 2DEG. 7 The device performance of photodetectors and transistors are normally determined by the optical transition nature and intrinsic effective mass, and therefore, a deep understanding of the fundamental properties of (Al x Ga 1Àx ) 2 O 3 alloying materials is critical. Despite a handful of reports on the bandgap modulation of (Al x Ga 1Àx ) 2 O 3 and demonstrations of modulationdoped HEMT, the experimentally obtained bandgap values exhibit a strong dependence on the synthesis methods and growth conditions.…”

“…For b-Ga 2 O 3 , similar values were reported, both theoretically 13,32 and experimentally (0.28 m e ). 33 Recently, the effective mass of the 2DEG formed at (Al x Ga 1Àx ) 2 O 3 /Ga 2 O 3 (x ¼ 0.2) interface is estimated to be 0.313 m e , 7 which is related to the strong electron-electron interaction. 34 The electronic band structure and bandgap modulation by Al incorporation can also be evaluated by absorption spectra.…”