Influence of SiN x Passivation on 2DEG Recovery and Current Collapse Suppression in Ultrathin‐Barrier HEMTs

Metal–insulator–semiconductor high‐electron‐mobility transistors (MIS‐HEMTs) were fabricated, and it was observed that in ultrathin‐barrier structures, the two‐dimensional electron gas (2DEG) density increased with the thickness of the silicon nitride (SiN x ) passivation layer deposited by low‐pressure chemical vapor deposition, eventually saturating at ~8 × 10 12 cm −2 . Beyond a critical thickness, while the 2DEG remained saturated, the current collapse behavior of the MIS‐HEMTs continued to be further suppressed with increasing SiN x thickness. Compared with devices incorporating thinner SiN x layers, those with thicker passivation exhibited a reduction in dynamic resistance by more than two orders of magnitude.