Improved Lifetime for Kilovolts Class Avalanche GaAs PCSS by Surface Passivation of Composite Dielectric Films

Avalanche gallium arsenide photoconductive semiconductor switchs (GaAs PCSSs) are essential solid-state semiconductor devices for realizing compact and repetitive-frequency pulsed power sources. However, the lifetime and reliability of avalanche GaAs PCSS face serious challenges due to ultrahigh-density current filaments and electric field concentration in the electrode region. Here, an aluminum nitride/silicon nitride (AlN/Si₃N₄) composite dielectric films are proposed dedicated to improve the lifetime of GaAs PCSS. The critical breakdown electric field strength, leakage current, and chemical element composition of the AlN/Si₃N₄ films are characterized. Meanwhile, the mechanism of leakage current of dielectric films is analyzed using Poole-Frenkel (P-F) emission and trap-assisted tunneling (TAT) mechanisms. Compared with the Si₃N₄–GaAs PCSS, the AlN/Si₃N₄–GaAs PCSS has 52.8% lower dark-state current, 10% higher current amplitude, and 7.3% higher lifetime at 40-kV bias voltage. Finally, the damage mechanism of GaAs PCSS was explored.