Abstract
This study examines the praseodymium-oxide- (Pr2O3-) passivated AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) with high dielectric constant in which the AlGaN Schottky layers are treated with P2S5/(NH4)2SX+ ultraviolet (UV) illumination. An electron-beam evaporated Pr2O3insulator is used instead of traditional plasma-assisted chemical vapor deposition (PECVD), in order to prevent plasma-induced damage to the AlGaN. In this work, the HEMTs are pretreated with P2S5/(NH4)2SXsolution and UV illumination before the gate insulator (Pr2O3) is deposited. Since stable sulfur that is bound to the Ga species can be obtained easily and surface oxygen atoms are reduced by the P2S5/(NH4)2SXpretreatment, the lowest leakage current is observed in MIS-HEMT. Additionally, a low flicker noise and a low surface roughness (0.38 nm) are also obtained using this novel process, which demonstrates its ability to reduce the surface states. Low gate leakage current Pr2O3and high-kAlGaN/GaN MIS-HEMTs, with P2S5/(NH4)2SX+ UV illumination treatment, are suited to low-noise applications, because of the electron-beam-evaporated insulator and the new chemical pretreatment.
Highlights
Because of their inherent high breakdown voltage (VBR ), high two-dimensional electron gas (2-DEG) concentration, and high saturation velocity [1, 2], and AlGaN/GaN high electron mobility transistors (HEMTs) are suitable to highpower and low-noise applications
To increase the efficiency of the P2 S5 /(NH4 )2 SX treatment, the treatment is performed in a UV chamber and both the high-k (ε ∼ 10) Pr2 O3 gate insulator and the passivating layer are deposited using electron-beam evaporation, which effectively prevents the plasma-induced generation of surface states
1.512 × 1013, 1087 cm2 /V-s for the standard treatment and (NH4 )2 SX + UV treatment for the devices. These results clearly demonstrate that P2 S5 /(NH4 )2 SX + UV treatment improves the channel mobility by reducing the number of surface traps
Summary
Because of their inherent high breakdown voltage (VBR ), high two-dimensional electron gas (2-DEG) concentration, and high saturation velocity [1, 2], and AlGaN/GaN high electron mobility transistors (HEMTs) are suitable to highpower and low-noise applications. Pretreatment before the deposition of the passivating layer between the source, the drain, and the gate terminals is dominated by the effect of surface traps, which cause flicker noise and current collapse problems. To increase the efficiency of the P2 S5 /(NH4 ) SX treatment, the treatment is performed in a UV chamber and both the high-k (ε ∼ 10) Pr2 O3 gate insulator and the passivating layer are deposited using electron-beam evaporation, which effectively prevents the plasma-induced generation of surface states. The (NH4 ) SX treatment effectively removes the native AlGaN surface oxide layer, it cannot prevent the increase in surface roughness that is caused by the alkaline (NH4 ) SX solution. A 10 nm-thick layer of praseodymium was firstly evaporated, using an optimal oxygen flow rate of 15 sccm During this stage, the chamber pressure was increased to around. Ti/Au (30 nm/300 nm) metals were deposited to form the interconnection and probe pads, and a 200 nm-thick SiO2
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