Large spin accumulation and crystallographic dependence of spin transport in single crystal gallium nitride nanowires.

Semiconductor spintronics is an alternative to conventional electronics that offers devices with high performance, low power and multiple functionality. Although a large number of devices with mesoscopic dimensions have been successfully demonstrated at low temperatures for decades, room-temperature operation still needs to go further. Here we study spin injection in single-crystal gallium nitride nanowires and report robust spin accumulation at room temperature with enhanced spin injection polarization of 9%.

Complementary spin transistor using a quantum well channel.

In order to utilize the spin field effect transistor in logic applications, the development of two types of complementary transistors, which play roles of the n- and p-type conventional charge transistors, is an essential prerequisite. In this research, we demonstrate complementary spin transistors consisting of two types of devices, namely parallel and antiparallel spin transistors using InAs based quantum well channels and exchange-biased ferromagnetic electrodes. In these spin transistors, the magnetization directions of the source and drain electrodes are parallel or antiparallel, respectively, depending on the exchange bias field direction.

Crystalline Direction Dependence of Spin Precession Angle and Its Application to Complementary Spin Logic Devices.

In a semiconductor channel, spin-orbit interaction is divided into two terms, Rashba and Dresselhaus effects, which are key phenomena for modulating spin precession angles. The direction of Rashba field is always perpendicular to the wavevector but that of Dresselhaus field depends on the crystal orientation. Based on the individual Rashba and Dresselhaus strengths, we calculate spin precession angles for various crystal orientations in an InAs quantum well structure.

Magnetic In x Ga 1 - x N nanowires at room temperature using Cu dopant and annealing.

Single-crystal, Cu-doped In x Ga1 - x N nanowires were grown on GaN/Al2O3 substrates via a vapor-liquid-solid (VLS) mechanism using Ni/Au bi-catalysts. The typical diameter of the Cu:In x Ga1 - x N nanowires was 80 to 150 nm, with a typical length of hundreds of micrometers. The as-grown nanowires exhibited diamagnetism.

Electric-field-induced spin injection enhancement.

The spin diffusion process can be modified by the electric field in a semiconductor channel. The electric field generated by the bias current improves the spin injection efficiency as well as the spin diffusion length at a ferromagnet-semiconductor hybrid system. Spin-polarized electrons from the ferromagnetic electrode were electrically investigated in an inverted heterostructure with an In0.

Gate-controlled spin-orbit coupling in InAs/InGaAs quantum well structures.

We have investigated gate electric field controlled Rashba spin-orbit coupling (SOC) constant (alpha) in In0.53Ga0.47As and InAs-inserted quantum well (QW) structures.

Synthesis of p-type GaN nanowires.

GaN has been utilized in optoelectronics for two decades. However, p-type doping still remains crucial for realization of high performance GaN optoelectronics. Though Mg has been used as a p-dopant, its efficiency is low due to the formation of Mg-H complexes and/or structural defects in the course of doping.

Thermal spin injection and accumulation in CoFe/MgO/n-type Ge contacts.

Understanding the interplay between spin and heat is a fundamental and intriguing subject. Here we report thermal spin injection and accumulation in CoFe/MgO/n-type Ge contacts with an asymmetry of tunnel spin polarization. Using local heating of electrodes by laser beam or electrical current, the thermally-induced spin accumulation is observed for both polarities of the temperature gradient across the tunnel contact.

Mouse model of Aspergillus and Alternaria induced rhinosinusitis.

Objective: Fungi are known to induce the production of chemical mediators from respiratory epithelial cells and have been increasingly recognized as important pathogens in sinusitis. However, the exact role of fungi in the pathogenesis of rhinosinusitis has not been clearly established. This study was performed to improve our understanding of the role of fungi in the pathogenesis of rhinosinusitis by developing an animal model of fungus induced rhinosinusitis.