Metal-insulator-metal (MIM) capacitors for DRAM applications have been realized using TiO2/ZrO2/TiO2 (TZT) and AlO-doped TZT (TZAZT and TZAZAZT) dielectric stacks. High capacitance densities of about 46.6 fF/μm2 (for TZT stacks), 46.2 fF/μm2 (for TZAZT stacks), and 46.8 fF/μm2 (for TZAZAZT stacks) have been achieved. Low leakage current densities of about 4.9×10−8 A/cm2, 5.5×10−9 A/cm2, and 9.7×10−9 A/cm2 (at -1 V) have been obtained for TZT, TZAZT, and TZAZAZT stacks, respectively. We analyze the leakage current mechanisms at different electric field regimes, and compute the barrier heights. The effects of constant current stress and constant voltage stress on the device characteristics are studied, and excellent device reliability is demonstrated. We compare the device performance of the fabricated capacitors with other stacked high-k MIM capacitors reported in recent literature.

A detailed analysis of leakage current density-gate voltage measurements of gate stacks composed of PLD grown ultra thin films of LaGdO3 (LGO) on p-type silicon substrates with 8.4 Å EOT is presented. Temperature dependent leakage measurements revealed that forward bias current was dominated by Schottky emission over trap assisted tunneling below 1.2 MV/cm and quantum mechanical tunneling above this field. The physical origin of the reverse bias current was found to be a combination of Schottky emission and trap assisted tunneling. Low leakage current densities in the range from 2.3×10-3 to 29×10-3 A/cm2 were recorded for films with EOT from 1.8 to 0.8 nm, that are at least four or more orders below the ITRS specifications and its SiO2 competitors.

Motivated by the unusual behavior of TiO2 films seen in electrical stress and defect annealing experiments, we studied the energy profile for forming a Frenkel defect in rutile TiO2, using first-principles calculations with a nudged-elastic-band method. We found strongly asymmetric diffusion barriers. The Frenkel pairs with small separation are exceedingly short-lived: the Ti interstitial position nearest to the the Ti vacancy is separated by only a 0.15eV barrier, and the next-nearest interstitial position is dynamically unstable. The formation enthalpies of Frenkel pairs with larger separation gradually vary between 4.2 and 5.0 eV, separated by 0.3-0.4eV barriers along the (001) direction. Contrary to some previous studies, we do not find Frenkel configurations with tetrahedrally bonded Ti interstitials. The very low barriers for Frenkel defect evolution are consistent with the observations from the electrical stress damage annealing experiments.

Nitridation of GeO2 interfacial layer (IL) was done using continuous wave (CW) and pulsed wave (PW) decoupled plasma nitridation (DPN) processes. Langmuir probe analysis of the N2 plasma demonstrates that at the same effective power and pressure, PW plasma has similar electron density (Ne) with lower electron temperature (kTe) and plasma potential (Vp) as compared to CW plasma. This results in softer plasma conditions using a PW process leading to lower plasma-related damage in the IL, but without reducing the overall nitrogen concentration. The plasma parameters were further correlated to mobility (μ) and interface trap density (Dit) extracted from fabricated Ge n-MOSFETs. As expected from the plasma analysis, at the same effective power and pressure, the PW DPN process shows 1.2X higher electron mobility as compared to a CW process. This improvement can enable GeON as an IL for future Ge CMOS gate stack technology.

High integrity SiO2/Al2O3 gate stack has been demonstrated for GaN metal-oxide-semiconductor (MOS) transistors. The SiO2 film formed on GaN by the microwave-excited plasma enhanced chemical vapor deposition (MW-PECVD) exhibits good properties compared that by the LP (Low Pressure)-CVD. Then, by incorporating the advantages of both of SiO2 with a high insulating and Al2O3 with good interface characteristics, the SiO2/Al2O3 gate stack structure has been employed in GaN MOS devices. The structure shows a low interface state density between gate insulator and GaN, a high breakdown field, and a large charge-to-breakdown by applying 3-nm Al2O3. The SiO2/Al2O3 gate stack has also been applied to AlGaN/GaN hybrid MOS heterojunction field-effect transistor (HFET) and the HFET shows excellent properties with the threshold voltage of 4.2 V and the maximum field-effect mobility of 192 cm2/Vs.

In this study, synthesis and characterization of rutile-Titanium dioxide (TiO2) thin films using pulsed DC Magnetron Sputtering at room temperature, along with the fabrication and characterization of MIM capacitors have been discussed. XPS and RBS data show that the films are stoichiometric and have compositional uniformity. The influence of electrode materials on electrical characteristics of the fabricated MIM capacitors has been studied. The Al/TiO2/Al based capacitors show low capacitance density (9 fF/μm2) with low dielectric constant (K=25) and high EOT (3.67 nm) due to low dielectric constant TiO2 phase formation on Al/Si substrate. On the other hand, Ru/TiO2/Ru based capacitors show high capacitance density (49 fF/μm2) with high dielectric constant (K=130) and low EOT (0.7nm) values at high frequency (100 KHz) due to high dielectric constant phase (rutile) formation of TiO2, on Ru/Si substrate. Raman spectra confirm that the films deposited on Ru/Si substrate show the rutile phase.

We investigated AlAs0.56Sb0.44 epitaxial layers lattice-matched to InP grown by molecular beam epitaxy (MBE). Silicon (Si) and tellurium (Te) were studied as n-type dopants in AlAs0.56Sb0.44 material. Similar to most Sb-based materials, AlAs0.56Sb0.44 demonstrates a maximum active carrier concentration around low-1018 cm-3 when using Te as a dopant. We propose the use of a heavily Si-doped InAlAs layer embedded in the AlAsSb barrier as a modulation-doped layer. The In0.53Ga0.47As/AlAs0.56Sb0.44 double heterostructures with a 10 nm InGaAs well show an electron mobility of about 9400 cm2/V・s at 295 K and 32000 cm2/V・s at 46 K. A thinner 5 nm InGaAs well has an electron mobility of about 4300 cm2/V・s at 295 K. This study demonstrates that AlAs0.56Sb0.44 is a promising barrier material for highly scaled InGaAs MOSFETs and HEMTs.