11:00 〜 11:50
▲ [18a-P04-14] Investigation of Tunneling Barriers for Si Spin-Valve Devices
キーワード：barrier layer, spin injection
In a spin transistor, it is necessary to inject spin carriers from a ferromagnetic source into a semiconductor channel. Due to the conductivity mismatch between metal and semiconductor, the spin injection efficiency is usually poor, and spin transistors with high spin-dependent output characteristics have not yet been realized. One of effective ways to improve the injection efficiency is to insert a layer of insulating material between the ferromagnetic source(drain) layer and the semiconductor channel, and use the quantum tunneling effect to improve the injection efficiency. As one of the most popular materials currently available, MgO has been studied, and shows a tunneling barrier of about 0.4 eV between Fe and MgO. However, a systematic study on the tunnel barrier height of various insulating materials in ferromagnetic layer / tunnel barrier / Si structure is still lacking.
In this study, we prepared samples of Fe/ tunnel barrier / n+Si substrate with different insulating materials (MgO, MgAl2O4, Al2O3) as the tunnel barrier, and studied their barrier height. Here, MgO layers were grown by either molecular beam epitaxy (MBE) or magnetron sputtering, MgAl2O4 layers were grown by magnetron sputtering, and Al2O3 layers were grown by atomic layer deposition (ALD). We fabricated diode structures of Fe/tunnel barrier/ n+Si and measured their I-V characteristics at 4.2 K, from which we calculated the barrier height using the Simmons model. As a result, at the barrier thickness of 1.5 nm, the barrier height is nearly the same for MgO (Sputter), MgAl2O4 (Sputter), and Al2O3 (ALD). Our results suggest that defect density in MgAl2O4 (Sputter) and Al2O3 (ALD) increases much faster than in MgO when the barrier thickness increases.
In this study, we prepared samples of Fe/ tunnel barrier / n+Si substrate with different insulating materials (MgO, MgAl2O4, Al2O3) as the tunnel barrier, and studied their barrier height. Here, MgO layers were grown by either molecular beam epitaxy (MBE) or magnetron sputtering, MgAl2O4 layers were grown by magnetron sputtering, and Al2O3 layers were grown by atomic layer deposition (ALD). We fabricated diode structures of Fe/tunnel barrier/ n+Si and measured their I-V characteristics at 4.2 K, from which we calculated the barrier height using the Simmons model. As a result, at the barrier thickness of 1.5 nm, the barrier height is nearly the same for MgO (Sputter), MgAl2O4 (Sputter), and Al2O3 (ALD). Our results suggest that defect density in MgAl2O4 (Sputter) and Al2O3 (ALD) increases much faster than in MgO when the barrier thickness increases.