Scattering analysis of 2DEG mobility in undoped and doped AlGaN/AlN/GaN heterostructures with an in situ Si 3 N 4 passivation layer

Improved Electrical Properties of AlGaN/GaN High-Electron-Mobility Transistors by In Situ Tailoring the SiNx Passivation Layer

“…In an AlGaN/GaN HEMT, the low-field 2DEG mobility is affected by diverse scattering mechanisms including electron–phonon, electron–electron, from line and point defects, interface-roughness (IFR), alloy, and piezoelectric (PE) scattering. ,− As reported by Zanato et al, the room-temperature drift mobility of the 2DEG is limited by the interaction of the electron with polar optical phonons that dominate above ∼125 K. ,, Below this temperature range, where optical phonon populations freeze out, PE and acoustic phonon scattering are the dominant mechanisms. In the lowest temperature range, the mobility is limited by IFR and strain field-deformation potential scattering or (uncharged dislocation scattering) with some contribution by acoustic phonons and PE scattering. ,− …”

“…1,6 Current flow within this region is affected by several growth-related factors such as interface roughness and local variations in alloy composition. 4,6,7 The polarization-induced 2DEG possesses a conjugate sheet of opposite charge at the top surface of the AlGaN barrier or thin GaN cap, 1,6,8 making the HEMT device highly sensitive to the surface states and any modification to the filling of donor-like surface states. 9 Any modulation to the surface states (degree of ionization), via stress−strain or passivation of the donor-like surface states, will impact the overall electrical properties of the structure.…”

“…The two-dimensional electron gas (2DEG) that is formed in AlGaN/GaN heterostructures, when grown in the traditional c -axis orientation, is the foundation of high-electron-mobility transistors (HEMTs) based on the group-III-nitride semiconductors. − The 2DEG primarily resides in the GaN at the interface with the thin (nominally 20 nm) AlGaN barrier layer. Along with band offset, the internal field within the 2DEG is affected by lattice mismatch and thermal strains. , Current flow within this region is affected by several growth-related factors such as interface roughness and local variations in alloy composition. ,, The polarization-induced 2DEG possesses a conjugate sheet of opposite charge at the top surface of the AlGaN barrier or thin GaN cap, ,, making the HEMT device highly sensitive to the surface states and any modification to the filling of donor-like surface states . Any modulation to the surface states (degree of ionization), via stress–strain or passivation of the donor-like surface states, will impact the overall electrical properties of the structure. − …”

Scattering analysis of ultrathin barrier (< 7 nm) GaN-based heterostructures

“…The transport properties of the 2DEG and the crystal quality are important in terms of the desired output characteristic of the device used [20]. Hence, these problems that may be occurred during the growth process in the crystal growth can be seriously affected the 2DEG transport properties.…”

AlGaN/GaN HEMT with LPCVD deposited SiN and PECVD deposited SiCOH low-k passivation

“…The stress applied on the AlGaN/GaN layer increases the density of two dimensional electron gas of HEMT as well as reduces the charge mobility due to the deformation of crystal structure and related scattering mechanisms. [26][27][28][29][30][31] The details should be further studied in the future work.…”