Temperature-Dependent Characteristics of GaN Homojunction Rectifiers

We report a homojunction gallium nitride (GaN) p-i-n rectifier fabricated on free-standing GaN substrates with the breakdown voltage 800 V and low specific ON-resistance (R_ONA). At 298 K, RONA is 0.28 mΩ-cm² at the current density (J) of 2.5 kA/cm² and the corresponding Baliga´s figure of merit is 2.5 GW/cm². At a given temperature, R_ONA values decrease with J due to conductivity modulation in the drift region. The ambipolar lifetime (τ_a) is also determined by open-circuit voltage decay measurement. The value for τ_a is 9.6 ns at 298 K and it monotonically increases to 22 ns at 448 K. The reverse I-V measurement reveals the reverse leakage current mechanism is mainly attributed to a field-assisted ionization process from deep-level centers in the space-charge region. The analysis of T-I-V curve yields the Poole-Frenkel coefficient (~3.1 × 10^-4 eV · V^-1/2 · cm^-1/2) and a deep-level trap (~0.7 eV) at zero bias.