LAUSR

GaN-based heterojunction bipolar transistors (HBTs) have great potential in the fields of radio frequency power amplifier and power switching applications. However, the surface etching damage of p-type base layer has posed significant challenges to implementing ohmic contact and low resistance, which is the major bottleneck in improving the current drive capability of GaN-based HBTs. In this work, n-AlGaN/p-InGaN/n-GaN double HBTs (DHBTs) featured with ultralow specific on-resistance and high output current density were successfully fabricated. To reduce the base resistance and improve the ohmic contact of the etched p-InGaN base, a maskless regrowth of heavily Mg-doped p++-InGaN contact layer by metal–organic chemical vapor deposition (MOCVD) was exploited. MOCVD thermal treatment was further adopted to recover the etching damages of the base layer by filling the nitrogen vacancies with active nitrogen atoms. The base resistance and surface recombination current of the p-InGaN base were both substantially reduced. As a result, the maximum output current density of the DHBTs with an emitter area of 40 × 40 μm2 was increased from 0.2 to 14 kA cm−2, and the specific on-resistance was decreased from 38 to 0.45 mΩ·cm2. This work paves the way for the practical application of GaN-based DHBTs.