Hafnium-doped GaN with n-type electrical resistivity in the 10−4 Ω cm range

Abstract

Hafnium (Hf) as an n-type dopant for group III nitride is proposed and investigated. Uniform doping of Hf into GaN realized an electrical resistivity as small as 7.89 × 10−4 Ω cm, which approaches that of a typical electron-beam deposited indium-tin oxide (ITO) thin film (∼3.75 × 10−4 Ω cm). Depending on doping level, the room-temperature (RT) donor activation energy for Hf in GaN was estimated to be in the range of 85-132.5 meV. Highly conductive Hf-doped GaN thin films with atomically smooth surface feature were achieved via Hf-delta doping, with RT electrical resistivity as small as 1.24 × 10−3 Ω cm. These highly conductive Hf-doped GaN films can be used as n-type transparent current-spreading layer (TCL) for large area light-emitting diodes (LEDs). With further improvement, highly conductive Hf-doped GaN has potential to be used as p-type TCL replacing the traditional indium-tin oxide for GaN-based LEDs.