Forward leakage currents in GaN p-i-n diodes

Excessive forward leakage currents in GaN p-i-n diodes were investigated. Traditional diffusion mechanism dominates at VF > 2 V. The effective band gap is derived to be ∼2.21 eV, which is much lower than 3.4 eV and attributed to a band fluctuation caused by dislocations; At 1.35 V < VF < 2 V, a trap-assisted tunneling process becomes important, whose ideality factor is still larger than 4.1 at T = 400 K; Two distinct power-law relationships were observed at lower biases, separated at VF = 0.8 V, whose exponents are extracted to be ∼8 and ∼4, respectively. The behavior is in a good agreement with the space-charge-limited model, featuring an exponentially decaying distribution of trap states below the conduction band.