A02 group

A02-1 Development of diamond electron device using III-nitride nanolaminate singularity structure

  • Principal Investigator / Yasuo Koide (National Institute for Materials Science / Executive Vice President)
  • Co-Investigator / Masataka Imura (National Institute for Materials Science / Senior Researcher)

Recently, a nanoscale multilayer material using Al2O3/TiO2, named by nanolaminate layer, has been reported to provide a high dielectric constant (k) larger than 1000 due to dielectric relaxation by Maxwell-Wagner effect. The purpose of this research is twofold. The first is to develop a singularity structure of the nanolaminate layer composed of dielectric i-AlN and conductive c-GaN with k larger than 100 and the respective 1 nm thickness. The second is to demonstrate a new-concept diamond transistor using this nanolaminate layer gate on hydrogenated (H) diamond surface. The hole carrier density in the H-terminated diamond surface is reported by our research group to be as large as 1014 cm-3 which is one-order of magnitude larger than that of commercialized AlGaN/GaN heterojuntion transistor. In order to control such the high-density hole carrier, it is required to develop the gate insulator with k larger than 100. The development of the AlN/GaN nanolaminate singularity structure is a key to success.

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A02-2 Research on novel light emitting devices by using the properties of singularity structure crystals

  • Principal Investigator / Hideki Hirayama (RIKEN / Chief Scientist)
  • Co-Investigator / Wataru Terashima (RIKEN / Researcher)
  • Co-Investigator / Norihiko Kamata (Saitama University / Professor)

In this work, we explore novel light emitting devices by introducing and using the properties of singularity structure crystals. In order to realize unexplored deep-ultraviolet (DUV) and terahertz (THz) light emitting devices, it is necessary to achieve a high hole concentration p-type AlGaN, a low dislocation density AlN buffer layer as well as AlGaN multi-stacking superlattices (SLs) with atomically flat hetero-interfaces. In this project, we will realize more than 50 % efficiency DUV light-emitting diodes (LEDs) and laser diodes (LDs) by developing pillar AlN array light extraction structure by using a self-assembling growth method and/or by developing high hole concentration p-AlGaN layers with co-doping in short-period superlattices (SPSLs). In order to achieve quantum-cascade lasers (QCLs), we need AlGaN/GaN multi-stacking SL structures with atomically flat hetero-interfaces. We will realize unexplored frequency THz-QCLs by developing high optical gain multi-stacking AlGaN/GaN high-quality SLs by using our original droplet elimination by thermal annealing (DEAT) growth method.

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A02-3 Characterization and control of GaN heterointerfaces including singularity structures for advanced electron devices

  • Principal Investigator / Tamotsu Hashizume (Hokkaido University / Professor)
  • Co-Investigator / Masamichi Akazawa (Hokkaido University / Associate Professor)
  • Co-Investigator / Taketomo Sato (Hokkaido University / Associate Professor)

GaN-based heterosystems utilizing various kinds of singularity structures and potential barriers will be high-level heterointerface continuum applicable to next-generation optical and electron devices. On the other hand, such hterointerfaces generally include high-density electronic states causing deterioration of device performances. To apply heterosystems utilizing singularity structures to high-performance devices, it is inevitable to characterize and control of interface electronic states in the vicinity of singularity structures.
In this project, we will precisely characterize electronic states of GaN-based heterosystems including singularity structures by a rigorous simulation of capacitance-voltage characteristics, transient capacitance methods and admittance analyses. From comparative studies between structural/chemical properties and electronic states, in addition, control schemes and/or processes for electronic states will be achieved.
For development of a novel electron device, we will fabricate a multi nanostructure having sidewall channels on a non-polar or a semi-polar GaN surface, as shown in the figure. In addition, we will develop novel sensor devices and ultralow resistance electrodes on the basis of nano-porous GaN structures prepared by an electrochemical process.


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