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.
Yan et al. (Thu,) studied this question.