Papers by Keyword: Hall Mobility

Abstract: Gated Hall measurements of lateral MOSFET devices can be used to directly measure the inversion layer free carrier density and carrier Hall mobility. From this measurement the total number of charged interface traps (N_IT) can be extracted. This provides useful insight into the degree of Coulomb scattering expected. By obtaining gated Hall data from 4° off-axis Si-face (0001) 4H-SiC MOSFETs with varied p-well doping levels, mobility limiting components can also be estimated. For these samples it is observed that interface trapped charge is almost half of the total inversion charge, and thus Coulomb scattering dominates at low Vgs or low transverse (or normal) effective field; while phonon scattering may dominate at moderate effective field, and surface roughness only limits mobility at gate fields higher than the rated usage, or at doping levels much higher than 2×10¹⁸ cm^-3.

Abstract: Silicon on insulator (SOI) wafer has allowed the integrated circuit (IC) industry to create superior, high-performance solutions. In addition, doping techniques are vital in the silicon sector due to the need to regulate the material electrical properties. The spin on dopant (SOD) approach is an alternative method that involves spinning a solution containing dopant onto SOI wafers. This research aims to determine the impact of thermal diffusion temperature and soaking time on sheet resistance of doped SOI wafer using SOD approach. Additionally, the homogeneity of doping was studied by utilizing mapping techniques. Three inches boron-doped SOI wafers were cut and cleaned according to Radio Corporation of America (RCA) standards. N-type dopants of Filmtronics SOD P509 were deposited on SOI wafer by using a spin coater, for 40 seconds at 4,000 revolutions per minute (rpm). The thermal diffusion temperature and soaking time were set between 700°C to 1000°C for 30 to 120 minutes. After thermal diffusion, hydrofluoric acids (HF) were diluted and used to etch samples. All materials were evaluated using a four-point probe, Hall Effect and Atomic Force Microscope (AFM). The results show that when the thermal diffusion soaking time increases, sheet resistance decreases until activated dopants are saturated. When sheet resistance decreases, dopant concentration rises. Temperature and soaking time increase carrier density and surface roughness, while decreasing Hall mobility. From mapping techniques, it shows low non-uniformity value which less than 10% suggests good thermal diffusion control.

Abstract: In the range 80 K-900 K, we have investigated the electrical properties of heavily aluminum in-situ doped, 4H-SiC samples. The temperature dependence of the hole concentration and Hall mobility was analyzed in the model taking into account heavy and light holes. The modelisation parameters were compared with experimental values of Secondary Ion Mass Spectroscopy (SIMS) and Capacitance-Voltage (CV) measurements.

Abstract: In this work, electrical properties of lateral n-channel MOSFETs implanted with differentnitrogen doses in the channel region were measured by Hall-effect technique at 300K. A mobility improvement with increasing nitrogen implantation doses is observed. Interface trap density (Dit) was determined from the experimentally measured Hall carrier density. Our results show a high Dit near and within the conduction band that does not change significantly when the nitrogen implantation dose is increased, despite observed mobility improvement.

Abstract: We have investigated the electrical properties of n-type 4H-SiC in-situ germanium-doped homoepitaxial layers grown by chemical vapor deposition. Germanium is an isoelectronic impurity and, therefore, not expected to contribute to the conductivity. However, Hall effect measurements taken on samples with and without germanium revealed an enhanced mobility by a factor of ≈2 at T ≈ 55 K in the germanium-doped sample despite equal free electron concentration and equal compensation. Deep level transient spectroscopy (DLTS) measurements taken on germanium-doped samples reveal negative peaks indicating the presence of charged extended defects.

Abstract: The impact of the thickness of an AlN spacer in AlGaN/AlN/GaN high electron mobility transistor (HEMT) structures on the Hall mobility was investigated in a range of 30 K - 340 K. The AlN spacer has a strong impact on the mobility at temperatures below 150 K. This effect is linked to a reduction of alloy scattering. Optical and scanning electron microscopy revealed hexagonal shaped defects which also have an effect on the mobility. These defects can be avoided by an appropriate adjustment of the AlN layer thickness.

Abstract: Effect of a shallow nitrogen implantation in the channel region of n-channel 4H-SiC Hall bar MOSFETs on their electrical properties has been characterized by Hall effect. A significant improvement of Hall mobility in normally-off devices is observed with increasing nitrogen implantation dose up to 10¹³ cm^-2 with a peak Hall mobility of 42.4 cm².V^-1.s^-1. Coulomb scattering as dominant scattering mechanism up to room temperature is demonstrated using temperature dependent MOS-Hall effect characterization.

Abstract: The p-type doping of high purity semi-insulating 4H-SiC by Al⁺ ion implantation and a conventional thermal annealing of 1950 °C/5 min has been studied for implanted Al concentration in the range of 1 x10¹⁹ - 8 x 10²⁰ cm^-3 (0.36 μm implanted thickness). Sheet resistance in the range of 1.6 x 10⁴ to 8.9 x10² Ω, corresponding to a resistivity in the range of 4.7 x 10^-1 to 2.7 x 10^-2 Ωcm for increasing implanted Al concentration have been obtained. Hall carrier density and mobility data in the temperature range of 140–600 K feature the transition from a valence band to an intra-band conduction for increasing implanted Al concentration. The specific contact resistance of Ti/Al contacts on the 5 x10¹⁹ cm^-3 Al implanted specimen features a thermionic field effect conduction with a specific contact resistance in the 10^-6 Ωcm2 decade.

Abstract: N-channel MOSFETs were manufactured on p-type and on p-implanted, n-type 4H-SiC substrates. The electron mobility in the inversion channel was measured to be correlated with the structural and chemical properties determined by transmission electron microscopy. With regard to what was previously discussed in the literature, interfacial layer formation and carbon distribution across the SiC/SiO2 interface were considered in relation with the measured Hall electron mobility.

Abstract: 4H-SiC presents great advantages for its use in power electronic devices working at particular conditions. However the development of MOSFETs based on this material is limited by mobility degradation. N-channel SiC MOSFETs were manufactured on p-type epitaxial and p-implanted substrates and the electron mobility in the inversion channels was measured to be correlated with their structural and chemical properties determined by transmission electron microscopy methods. With regard to what was previously discussed in the literature, transition layer formation and carbon distribution across the SiC-SiO₂ interface are considered in relation with the measured low electron mobility of the MOSFETS.