Takuya Hoshii

Individual Atomic Imaging of Multiple Dopant Sites in As-Doped Si Using Spectro-Photoelectron Holography

The atomic scale characterization of dopant atoms in semiconductor devices to establish correlations with the electrical activation of these atoms is essential to the advancement of contemporary semiconductor process technology. Spectro-photoelectron holography combined with first-principles simulations can determine the local three-dimensional atomic structures of dopant elements, which in turn affect their electronic states. In the work reported herein, this technique was used to examine arsenic (As) atoms doped into a silicon (Si) crystal. As 3d core level photoelectron spectroscopy demonstrated the presence of three types of As atoms at a total concentration of approximately 1020 cm-3, denoted as BEH, BEM, and BEL. On the basis of Hall effect measurements, the BEH atoms corresponded to electrically active As occupying substitutional sites and exhibiting larger thermal fluctuations than the Si atoms, while the BEM atoms corresponded to electrically inactive As embedded in the AsnV (n = 2-4) type clusters. Finally, the BEL atoms were assigned to electrically inactive As in locally disordered structures.

Formation of Mo 2 C electrodes using stacked sputtering process for thermally stable SiC Schottky barrier diodes

The introduction of SiC Schottky barrier diodes has enabled further power loss reduction in high voltage power electronics, owing to its high operation speed [1]. Various electrode materials for diodes have been reported so far, including Mo, Ti and Ni [2]. However, interface reactions between these metals and SiC surfaces results in the formation of an inhomogeneous interface, which rises concerns to long-term reliability issues. Mo2C electrodes, on the other hand, have revealed stable diode characteristics against an annealing up to 1050 °C, suggesting practically reliable operations in power electronics [3]. Although nice electrical characteristics were obtained, the physical analyses of the interface are still yet to be done. In this presentation, detailed analyses of the formation of a Mo2C layer on SiC surfaces using stacked sputtering process are reported [4].

Low temperature ohmic contact for p-type GaN using Mg electrodes

Low Ohmic contact for p-type GaN (pGaN) has been of great importance for various applications including light emitting diodes and nitride based power devices. Although a low contact resistance (ρc) of the order of 10−6 Ωcm2 can be obtained with air-annealed Au/Ni electrodes, the hole transport relies on NiO islands inhomogeneously formed between the Au and the pGaN surface, giving concerns in long term reliability [1]. For Ti-based electrodes, on the other hand, an Ohmic contact can be achieved by forming an intermixed layer at the interface of the metal and pGaN surface, yet a relatively high temperature is required. Moreover, the ρc is reported to degrade along with time due to in-diffusion of hydrogen atoms stored in the metal layer during the high temperature annealing [2].

3D scaling for insulated gate bipolar transistors (IGBTs) with low V ce(sat)

Three dimensionally (3D) scaled IGBTs that have a scaling factor of 3 (k=3) with respect to current commercial products (k=1) were fabricated for the first time. The scaling was applied to the lateral and vertical dimensions as well as the gate voltage. A significant decrease in ON resistance, — Vce(sat) reduction from 1.70 to 1.26 V — was experimentally confirmed for the 3D scaled IGBTs.