(The)Political economy of strategic economic cooperation and alliances : the cases of the U.S.-Israel and U.S.-Australia FTA

학위논문(석사)--서울대학교 대학원 :외교학과,2007.Maste

Impact of Sulfur Passivation on Carrier Transport Properties of In0.7Ga0.3As Quantum-Well MOSFETs

We investigated the impact of a sulfur passivation (S-passivation) process step on carrier transport properties of surface-channel In0.7Ga0.3As quantum-well (QW) Metal-Oxide-Semiconductor Field-Effect-Transistors (MOSFETs) with source/drain (S/D) regrowth contacts. To do so, we fabricated long-channel In0.7Ga0.3As QW MOSFETs with and without (NH4)2S treatment prior to a deposition of Al2O3/HfO2 = 1-nm/3-nm by atomic-layer-deposition (ALD). The devices with S-passivation exhibited a lower value of subthreshold-swing (S) = 74 mV/decade and more positive shift in the threshold voltage (VT) than those without S-passivation. From the perspective of carrier transport, S-passivated devices displayed excellent effective mobility (μeff ) in excess of 6,300 cm2/V·s at 300 K. It turned out that the improvement of μeff was attributed to reduced Coulombic and surface-roughness scatterings. Using a conductance method, a fairly small value of interface trap density (Dit) = 1.56 × 1012 cm?2eV?1 was obtained for the devices with S-passivation, which was effective in mitigating the Coulombic scattering at the interface between the high-k dielectric layer and the In0.7Ga0.3As surface-channel layer

Sub-30-nm In0.8Ga0.2As Composite-Channel High-Electron-Mobility Transistors With Record High-Frequency Characteristics

We present sub-30-nm In0.8Ga0.2As composite-channel high-electron-mobility transistors (HEMTs) with outstanding dc and high-frequency characteristics. We adopted a composite-channel design with an In0.8Ga0.2As core layer, which led to superior carrier transport properties such as a Hall mobility (μn_Hall) of 13 500 cm2/V·s. The device with Lg = 19 nm exhibited an excellent combination of dc and RF properties, including RON = 271-μm, gm_max = 2.8 mS/μm, and fT/fmax = 738/492 GHz. To understand the physical origin of such an excellent combination of dc and RF responses,we analyzed the effective mobility (μn_eff) and delay time for both longand short-Lg devices, revealing a very high μn_eff value of 13 200 cm2/V·s and an average velocity under the gate (vavg) of 6.2 × 107 cm/s. We also studied the impact of the electrostatic integrity of the device, finding that the intrinsic output conductance (goi) played a role in determining fT and fmax in short-Lg HEMTs