10B Conformal Doping for Highly Efficient Thermal Neutron Detectors.

This paper reports a simple and novel conformal doping strategy for microstructured silicon diodes using enriched 10B for sidewall doping while enabling enhanced neutron sensitivity. Monte-Carlo nuclear particle (MCNP) code simulations were initially used to calculate the neutron detection efficiency in the microstructured diodes as a function of geometry and pitch. A high-temperature anneal in 10B-filled diodes results in a conformal silicon p+ layer along the side walls of the trenches in the diodes. This results in large neutron detection areas and enhanced neutron detection efficiency when compared with planar detectors. With the method discussed here, a thermal neutron detection of ∼21% efficiency is achieved, which is significantly higher than the efficiency achieved in planar detectors (∼3.5%). The higher efficiency is enabled by the 10B acting as a source for conformal doping in the trenches, resulting in lower leakage current while also enabling neutron sensitivity in the microstructured diodes.

Recent Developments in p-Type Oxide Semiconductor Materials and Devices.

The development of transparent p-type oxide semiconductors with good performance may be a true enabler for a variety of applications where transparency, power efficiency, and greater circuit complexity are needed. Such applications include transparent electronics, displays, sensors, photovoltaics, memristors, and electrochromics. Hence, here, recent developments in materials and devices based on p-type oxide semiconductors are reviewed, including ternary Cu-bearing oxides, binary copper oxides, tin monoxide, spinel oxides, and nickel oxides. The crystal and electronic structures of these materials are discussed, along with approaches to enhance valence-band dispersion to reduce effective mass and increase mobility. Strategies to reduce interfacial defects, off-state current, and material instability are suggested. Furthermore, it is shown that promising progress has been made in the performance of various types of devices based on p-type oxides. Several innovative approaches exist to fabricate transparent complementary metal oxide semiconductor (CMOS) devices, including novel device fabrication schemes and utilization of surface chemistry effects, resulting in good inverter gains. However, despite recent developments, p-type oxides still lag in performance behind their n-type counterparts, which have entered volume production in the display market. Recent successes along with the hurdles that stand in the way of commercial success of p-type oxide semiconductors are presented.

P-type Cu(2)O/SnO bilayer thin film transistors processed at low temperatures.

P-type Cu2O/SnO bilayer thin film transistors (TFTs) with tunable performance were fabricated using room temperature sputtered copper and tin oxides. Using Cu2O film as capping layer on top of a SnO film to control its stoichiometry, we have optimized the performance of the resulting bilayer transistor. A transistor with 10 nm/15 nm Cu2O to SnO thickness ratio (25 nm total thickness) showed the best performance using a maximum process temperature of 170 °C. The bilayer transistor exhibited p-type behavior with field-effect mobility, on-to-off current ratio, and threshold voltage of 0.66 cm(2) V(-1) s(-1), 1.5×10(2), and -5.2 V, respectively. The advantages of the bilayer structure relative to single layer transistor are discussed.

Record mobility in transparent p-type tin monoxide films and devices by phase engineering.

Here, we report the fabrication of nanoscale (15 nm) fully transparent p-type SnO thin film transistors (TFT) at temperatures as low as 180 °C with record device performance. Specifically, by carefully controlling the process conditions, we have developed SnO thin films with a Hall mobility of 18.71 cm(2) V(-1) s(-1) and fabricated TFT devices with a linear field-effect mobility of 6.75 cm(2) V(-1) s(-1) and 5.87 cm(2) V(-1) s(-1) on transparent rigid and translucent flexible substrates, respectively. These values of mobility are the highest reported to date for any p-type oxide processed at this low temperature. We further demonstrate that this high mobility is realized by careful phase engineering. Specifically, we show that phase-pure SnO is not necessarily the highest mobility phase; instead, well-controlled amounts of residual metallic tin are shown to substantially increase the hole mobility. A detailed phase stability map for physical vapor deposition of nanoscale SnO is constructed for the first time for this p-type oxide.