Wafer Fusion Technique Applied to GaN/GaN System

Abstract

The wafer fusion technique is applied to a GaN/GaN system for the first time. The processing conditions for successful wafer fusion are clarified. The lowest annealing temperature for successful fusion of GaN/GaN is 500 • C. It is found that surface smoothness and a large weighting pressure are essential to achieve both a uniform interface and better reproducibility. The electric property of the fused interface is also characterized. Current-voltage (I -V ) characteristics of the n-GaN/n-GaN and p-GaN/p-GaN fused interface reveal that a pinning effect of the Fermi level exists at the fused interface.

n- AlGaAs /p- GaAs /n -GaN heterojunction bipolar transistor wafer-fused at 550–750 °C

“…͑Given the thermal stability of GaN, GaN fusion has been reported at temperatures up to 1000°C͒. [3][4][5] The studies described here reveal that fusion temperatures as low as 550°C can be used to produce GaAs-GaN HBTs with electrically active fused interfaces. In fact, the device characteristics of the HBT improve with reduced fusion temperature.…”

Interface structure and adhesion of wafer-bonded GaN/GaN and GaN/AlGaN semiconductors

“…[3][4][5][6] Direct wafer bonding has been reported to be an ideal approach to integrate mismatched materials and has been used to fabricate a number of advanced microelectronic or photonic devices. 3,4,6,7 Wafer bonding of GaN and other related semiconductors has been reported by a few research groups, such as GaN/GaAs, 3,4 GaN/InP, 6 and GaN/GaN. 7 However, to date, only a little effort has been focused on understanding the correlations among bonding process, wafer surface or interface microstructures, and interface adhesion.…”

“…3,4,6,7 Wafer bonding of GaN and other related semiconductors has been reported by a few research groups, such as GaN/GaAs, 3,4 GaN/InP, 6 and GaN/GaN. 7 However, to date, only a little effort has been focused on understanding the correlations among bonding process, wafer surface or interface microstructures, and interface adhesion. This work reports on the progress toward characterizing the surface microstructures and interface adhesion of wafer-bonded GaN and Al 0.25 Ga 0.75 N semiconductors.…”

Characterization of Ga-face/Ga-face and N-face/N-face interfaces with antiparallel polarizations fabricated by surface-activated bonding of freestanding GaN wafers

“…21) The electronic properties of wafer-fused Ga-face-to-Ga-face GaN/GaN interfaces were investigated. 22) In these previous works, segregation of Ga was observed in the bonding interfaces because the process temperature was too high. 18) In addition, occurrence of Fermi level pinning at interfaces was suggested, 22) which means that effects of antiparallel polarizations and impacts of interface states should be separately discussed.…”

“…22) In these previous works, segregation of Ga was observed in the bonding interfaces because the process temperature was too high. 18) In addition, occurrence of Fermi level pinning at interfaces was suggested, 22) which means that effects of antiparallel polarizations and impacts of interface states should be separately discussed. We previously reported for SAB-based interfaces made of other semiconductors that interface states were formed because of FAB irradiation, and their density hence the electrical properties of interfaces were sensitive to the post-bonding annealing.…”