Demonstration of atmospheric plasma activated direct bonding of N-polar GaN and β-Ga2O3 (001) substrates

Abstract

Direct wafer bonding of β-Ga2O3 and N-polar GaN at a low temperature was achieved by acid treatment and atmospheric plasma activation. The β-Ga2O3/GaN surfaces were atomically bonded without any loss in crystalline quality at the interface. The impact of post-annealing temperature on the quality of bonding interfaces was investigated. Post-annealing at temperatures higher than 700 °C increases the area of voids at bonded interfaces probably due to the difference in the coefficient of thermal expansion. The integration of β-Ga2O3 on the GaN substrate achieved in this work is one of the promising approaches to combine the material merits of both GaN and Ga2O3 targeting the fabrication of novel GaN/β-Ga2O3 high-frequency and high-power electronics as well as optoelectronic devices.

Electrical and Structural Analysis of β‐Ga2O3/GaN Wafer‐Bonded Heterojunctions with a ZnO Interlayer

“…In our previous work on the direct bonding of Ga 2 O 3 and N‐polar GaN, only ≈40% contact area was bonded and Newton's rings were observed where the surfaces were not in contact with each other. [ 25 ] Here, the surfaces were fully bonded. No Newton's rings were observed on the sample indicating a flat and clean interface.…”

“…Previously, we reported the direct bonding of β ‐Ga 2 O 3 and N‐polar GaN single crystal substrates. [ 25 ] We showed that the β ‐Ga 2 O 3 /GaN surfaces were atomically bonded without any readily identifiable loss in crystalline quality at the interface. [ 25 ] However, the bonded area was only ≈40% and the yield was lower than 50% probably because both GaN and Ga 2 O 3 have high mechanical hardness and any nano‐ or micro‐roughness on the surface would lead to non‐uniform bonding.…”

“…[ 25 ] We showed that the β ‐Ga 2 O 3 /GaN surfaces were atomically bonded without any readily identifiable loss in crystalline quality at the interface. [ 25 ] However, the bonded area was only ≈40% and the yield was lower than 50% probably because both GaN and Ga 2 O 3 have high mechanical hardness and any nano‐ or micro‐roughness on the surface would lead to non‐uniform bonding. Our experiments showed that the bonding yield is also affected by cleavage planes in the Ga 2 O 3 substrate with (001) orientation.…”