Dual‐Layer Semi‐Insulating GaN Substrates Doped with Fe, C, or Mn

The compatibility of impurity doping and the suppression of residual stress are crucial for fabricating a semi‐insulating GaN (SI‐GaN) substrate. Herein, a new method to fabricate several SI‐GaN substrates, including a dual‐layer SI‐GaN substrate comprising upper ≈100 μm‐thick GaN doped with Fe, C, or Mn and a lower ≈300 μm‐thick unintentionally doped GaN, using hydride vapor‐phase epitaxy is proposed. As a result, substrates doped with Fe, C, or Mn are successfully produced without cracks and pits. Resistivities around a doping concentration of ≈10 18 cm −3 are up to 6.6 × 10 8 , >10 12 , and >10 12 Ω cm at room temperature, respectively. The residual stress of the dual‐layer SI‐GaN film is also evaluated.