N-polar GaN/AlGaN/AlN high electron mobility transistors on single-crystal bulk AlN substrates

Abstract

Recent observation of high density polarization-induced two-dimensional electron gases in ultra-thin N-polar GaN layers grown on single-crystal AlN has enabled the development of N-polar high electron mobility transistors (HEMTs) on AlN. Such devices will take advantage of thermal and power handling capabilities of AlN, while simultaneously benefitting from the merits of N-polar structures, such as a strong back barrier. We report the experimental demonstration of N-polar GaN/AlGaN/AlN HEMTs on single-crystal AlN substrates, showing an on-current of 2.6 A/mm with a peak transconductance of 0.31 S/mm. Small-signal RF measurements revealed speeds exceeding ft/ fmax = 68/100 GHz. These results pave the way for developing RF electronics with excellent thermal management based on N-polar single-crystal AlN.

Density Functional Theory Study of Polarization-Induced Electron Confinement by Dilute Boron Alloying in ε-Ga2O3 Nanometer-Thick Film for High Electron Mobility Transistor

“…Ga 2 O 3 possesses five polymorphs, specifically α, β, γ, δ, and ε. Among these, the ε-phase is noted for its remarkable polarization property, which is an order of magnitude greater than GaN, a semiconductor material typically employed in high electron mobility transistors (HEMTs). , The findings on polarization of ε-phase Ga 2 O 3 have piqued the interest of numerous researchers that are exploring the possibilities of ε-Ga 2 O 3 based devices. − Chen et al have reported on the polarization switching properties of κ-Ga 2 O 3 (where κ and ε denote the same phase of Ga 2 O 3 ) in κ-Ga 2 O 3 /GaN heterostructure, revealing a remanent polarization of approximately 2.7 μC/cm 2 . Wang et al have indicated that the interface of ε-Ga 2 O 3 / m -GaN ( m -AlN) could achieve a high two-dimensional electron gas (2DEG) density of 10 14 cm –2 .…”

Surface Control of AlN Single Crystal Growth on SiC Substrate

“…As a direct bandgap semiconductor with a wide bandwidth of 6.2 eV and a high breakdown field strength (>1.2 × 10 6 V·cm –1 ), it has a large thermal conductivity (285 W·m –1 ·K –1 at 300 K), and the lattice parameters and the thermal expansion coefficient of AlN well match to GaN or Al x Ga (1– x ) N. , High-quality single-crystal AlN substrates are expected to greatly reduce defect densities in overgrown device structures, improving the performance and lifetime of devices. Due to these superior properties, there are many applications of AlN substrate that have been implemented or are being explored, including deep-ultraviolet photoelectric devices , and electronics operating at high-power, high-frequency, and high-temperature environments. ,− …”

Improvement of electrical properties by insertion of AlGaN interlayer for N-polar AlGaN/AlN structures on sapphire substrates

“…[18][19][20] Recently, an N-polar GaN/AlGaN/AlN HEMT was demonstrated using MBE. 21) Metal-organic vapor-phase epitaxy (MOVPE) is a promising growth technique for the mass production of nitride semiconductors. However, the fabrication of N-polar-surface GaN/AlN structures using MOVPE is problematic.…”