Studies on High-Voltage GaN-on-Si MIS-HEMTs Using LPCVD Si3N4 as Gate Dielectric and Passivation Layer

This paper investigates the performance of AlGaN/gallium nitride (GaN) MIS high electron mobility transistors (MIS-HEMTs). The gate dielectric layer and the surface passivation layer are formed by the low-pressure chemical vapor deposition (LPCVD) Si3N4. The LPCVD-Si3N4 MIS-HEMTs exhibit a high breakdown voltage (BV) of 1162 V at I-DS = 1 mu A/mm, a low OFF-state leakage of 7.7 x 10(-12) A/mm, and an excellent ON/OFF-current ratio of similar to 10(11). Compared with the static ON-resistance of 2.88 m Omega . cm(2), the dynamic ON-resistance after high OFF-state drain bias stress at 600 V only increases to 4.89 m Omega . cm(2). The power device figure of merit = BV2/R-ON.sp is calculated to be 469 MW . cm(-2). The LPCVD-Si3N4/GaN interface state density is in the range of (1.4-5.3) x 10(13) eV(-1) cm(-2) extracted by the conventional conductance method. Finally, the gate insulator degradation of GaN-based MIS-HEMTs is analyzed by time-dependent dielectric breakdown test. The lifetime is extrapolated to 0.01% of failures after ten years at 300 K by fitting the data with a power law to a gate voltage of 10.1 V

Fabrication of normally-off AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors by photo-electrochemical gate recess etching in ionic liquid

We characterized an ionic liquid (1-butyl-3-methylimidazolium nitrate, C8H15N3O3) as a photo-electrochemical etchant for fabricating normally-off AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs). Using the ionic liquid, we achieved an etching rate of similar to 2.9 nm/min, which is sufficiently low to facilitate good etching control. The normally-off AlGaN/GaN MIS-HEMT was fabricated with an etching time of 6 min, with the 20 nm low-pressure chemical vapor deposition (LPCVD) silicon nitride (Si3N4) gate dielectric exhibiting a threshold voltage shift from -10 to 1.2 V, a maximum drain current of more than 426 mA/mm, and a breakdown voltage of 582V. (C) 2016 The Japan Society of Applied Physic

不同粒径保水剂吸水特性及其对土壤物理性能的影响/Water Absorbent Capacity of Super Absorbent Polymer with Different Granularities and Its Effect on Soil Physical Properties[J]

通过室内试验,对大粒径（2.0～3.2 mm）、中粒径（1.0～2.0 mm）和小粒径（0.5～1 mm）3种粒径保水剂的吸水特性进行了测定,同时对施加不同粒径保水剂前后的沙质土壤的理化性质进行对比分析。结果表明：①保水剂的吸水倍率与其粒径大小呈负相关关系;②保水剂对土壤水分蒸发有明显的抑制效应,能显著提高土壤的水分含量;③保水剂会使土壤pH和电导率升高,降低土壤渗透性,土壤中液相比例增加的同时气相比例会相应减少。综合考虑3种不同粒径保水剂对土壤理化性质的影响,中粒径保水剂改善效果最好,在施用量为0.1%时,对土壤的改良效果最为明显,亦不会产生明显副作用