Impact of the Location of Iron Buffer Doping on Trap Signatures in GaN HEMTs

This paper presents the impact of two different iron (Fe) doping depths in the buffer, on trapping effects in AlGaN/GaN high electron mobility transistors (HEMTs). Drain current transient (DCT) measurements are performed on AlGaN/GaN HEMTs of 0.15-μm ultrashort gate length and 6 × 50 μm gate width at various chuck temperatures ranging between 25°C and 125°C. On the basis of these measurements we demonstrate that, for the devices under investigation 1) depending on the location of Fe doping in the buffer, number of trap signatures differ and 2) it influences the capture time and recovery time of the traps. This study demonstrates the effect of Fe doping depth on DCT visible only for temperatures more than 75°C. For a device with deeper level of Fe doping in the buffer, we find signatures of two traps with ac tivation energies of 0.55eV and 0.45eV. Whereas, another device with a shallow level of Fe doping in the buffer, has only one trap signature with activation energy 0.5eV.