Electron channel mobility in silicon-doped Ga₂O₃ MOSFETs with a resistive buffer layer

Abstract

The electron mobility in depletion-mode lateral β-Ga2O3(010) metal–oxide–semiconductor field-effect transistors (MOSFETs) with an n-channel formed by Si-ion (Si+) implantation doping was extracted using low-field electrical measurements on FET structures. An undoped Ga2O3 buffer layer protected the channel against charge compensation by suppressing outdiffusion of deep Fe acceptors from the semi-insulating substrate. The molecular beam epitaxy growth temperature was identified as a key process parameter for eliminating parasitic conduction at the buffer/substrate growth interface. Devices with a resistive buffer showed room temperature channel mobilities of 90–100 cm2 V−1 s−1 at carrier concentrations of low- to mid-1017 cm−3, with small in-plane mobility anisotropy of 10–15% ascribable to anisotropic carrier scattering.

Electron mobility in monoclinic β-Ga2O3—Effect of plasmon-phonon coupling, anisotropy, and confinement

“…The anisotropy is about 20% at a moderate doping. Such anisotropy is experimentally observed [32], but its origin is not clearly understood since it is well known that the electronic bands in β-Ga2O3 near the Γ point is isotropic. We attribute this anisotropy of the long-range interaction between the electrons and the LO modes (even in absence of any plasmon).…”

Assessment of phonon scattering-related mobility in β-Ga2O3

“…It is generally recognized that the bottom of the conduction band (CB), at the gamma point of the Brillouin zone, is essentially parabolic and spherical, with minor differences in the effective masses for the different k directions [24,25]. The scattering mechanism anisotropy is also expected to be moderate, as demonstrated by mobility measurements in MOSFETs with different channel orientations for which the mobility was statistically contained within 10%-15% [26]. Theoretically, the mobility anisotropy of β-Ga 2 O 3 was predicted to be within 30% for low-doped β-Ga 2 O 3 [23].…”

Impact ionization in β-Ga2O3

“…Based on the hypothetical electric field profile, the critical electric fields are evaluated under the limit αn≈αp and is also listed on Table-I. As revealed in a previous work [45] by the current authors and also from experimental observations [46] the electron mobility is slightly lower in the x direction compared to that in y. But considering the joint effect of on-resistance and breakdown field, transport along x direction is supposed to provide a higher Baliga's figure of merit [47].…”