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We systematically investigated characteristics of Pt-gated capacitors with four kinds of gate insulators such as Hf0.57Si0.43Ox, Hf0.64Si0.36Ox, HfO2, and Al2O3. The Hf0.64Si0.36Ox films fabricated by post-deposition annealing (PDA) at 800degC in O2 (PDO), N2(PDN), and 3% H2 (PDH) ambient exhibited quite different characteristics. After PDO, the Hf0.64Si0.36Ox film was partially crystallized and had a thick interfacial layer at the n-GaN/Hf0.64Si0.36Ox interface, while the Hf0.64Si0.36Ox films after PDN and PDH maintained an amorphous structure. The PDH capacitor exhibited an order of magnitude larger interface state density than the PDN capacitor, indicating that the PDN process can produce superior Hf0.64Si0.36Ox film. The Hf0.57Si0.43Ox,Hf0.64Si0.36Ox, HfO2, and Al2O3 films after PDA at 800degC in N2 were 15.4, 15.9, 17.6, and 9, respectively. The HfO2 and Al2O3 films consist of polycrystalline structure while the Hf0.57Si0.43Ox and Hf0.64Si0.36Ox films maintain an amorphous structure. The different structure strongly affected to electrical properties. The Hf0.57Si0.43Ox and Hf0.64Si0.36Ox capacitors showed superior electrical properties such as a minimal flatband voltage (Vfb) hysteresis ( [?] +70 mV) and a small Vfb shift ( [?] -0.46 V), as well asa low interface state density (~ 3 x 1011 cm-2eV-1 at -0.45 eV fromconduction band), and a high breakdown electric field ( [?] 8.6 MV/cm) compared to those of the HfO2 and Al2O3 capacitors.

We systematically investigated characteristics of Pt-gated capacitors with four kinds of gate insulators such as Hf0.57Si0.43Ox, Hf0.64Si0.36Ox, HfO2, and Al2O3. The Hf0.64Si0.36Oxfilms fabricated by post-deposition annealing (PDA) at 800°C in O2(PDO), N2(PDN), and 3% H2(PDH) ambient exhibited quite different characteristics. After PDO, the Hf0.64Si0.36Oxfilm was partially crystallized and had a thick interfacial layer at the n-GaN/Hf0.64Si0.36Oxinterface, while the Hf0.64Si0.36Oxfilms after PDN and PDH maintained an amorphous structure. The PDH capacitor exhibited an order of magnitude larger interface state density than the PDN capacitor, indicating that the PDN process can produce superior Hf0.64Si0.36Oxfilm. The Hf0.57Si0.43Ox,Hf0.64Si0.36Ox, HfO2, and Al2O3films after PDA at 800°C in N2were 15.4, 15.9, 17.6, and 9, respectively. The HfO2and Al2O3films consist of polycrystalline structure while the Hf0.57Si0.43Ox and Hf0.64Si0.36Oxfilms maintain an amorphous structure. The different structure strongly affected to electrical properties. The Hf0.57Si0.43Oxand Hf0.64Si0.36Oxcapacitors showed superior electrical properties such as a minimal flatband voltage (Vfb) hysteresis ( ≤ +70 mV) and a small Vfbshift ( ≤ -0.46 V), as well asa low interface state density (~ 3 × 1011cm-2eV-1at -0.45 eV fromconduction band), and a high breakdown electric field ( ≥ 8.6 MV/cm) compared to those of the HfO2and Al2O3capacitors.

Characteristics of hafnium silicate as gate dielectric in n-GaN capacitors were investigated. The Hf0.57Si0.43Ox, Hf0.64Si0.36Oxand HfO2films exhibited high dielectric constants of 15.4, 15.9, and 17.6, respectively. The Hf0.57Si0.43Oxand Hf0.64Si0.36Oxfilms, which had an amorphous structure, showed superior properties, including a minimal flatband voltage (Vfb) hysteresis (?70 mV) and a small Vfbshift (??0.45 V), as well as a low interface state density(~4 × 1011cm?2eV?1at ?0.4 eV from conduction band), and a high breakdown electric field (?8.6 MV cm?1) compared to those of a polycrystalline HfO2film.

We examine the energy band diagram at the n-type GaN (n-GaN)/SiO2interface and show that electron transfer from n-GaN to SiO2leads to the formation of negatively charged oxygen vacancies in the SiO2, resulting in the self-formation of an n-GaN/Ga2O3/SiO2structure. On the other hand, it is difficult to automatically form Ga2O3at a p-type GaN (p-GaN)/SiO2interface. This electron-transfer-induced self-formation of Ga2O3causes an interface dipole, which leads to band bending, resulting in an increase in the conduction band offset between GaN and SiO2. Accordingly, by using this self-forming phenomenon, GaN MOSFETs with lower leakage current can be realized.