Report of GaN HEMTs on 8-in Sapphire

The two crucial factors of large scale and high voltage can hardly be balanced for the traditional GaN HEMTs on Si substrates. Recently, one promising solution, GaN-on-sapphire, has attracted great attention. However, the commercialized GaN-on-sapphire wafers ever reported are usually 6 in. It is urgent to develop 8-in GaN-on-sapphire to reduce the cost and meet the market demands. In this work, to the best of our knowledge, an 8-in GaN-on-sapphire wafer is demonstrated for the first time. The sheet resistance
${R}_{\Box }$
exhibits a wafer-level nonuniformity of 4% and an average value of
$310 \, \boldsymbol {\Omega } /\Box $
, and the warpage is kept to
$30 \, \mu $
m, by dedicatedly tuning the 1.98-
$\mu $
m buffer stack. The fabricated 200-V HEMTs exhibit a low
${R}_{\text {ON}}$
of
$6.5 \, \boldsymbol {\Omega } \cdot \text {mm}$
, a
${V}_{\text {TH}}$
of -4.2 V, and an off-state breakdown voltage above 500 V without any field plate. The electrical mapping visualizes
${R}_{\text {ON}}$
and
${V}_{\text {TH}}$
distributed in concentric circles across the wafer. Generally, this work demonstrates the feasibility of realizing 8-in GaN-on-sapphire for power electronics applications in the future.