成果報告書詳細
管理番号20160000000798
タイトル*平成27年度中間年報 低炭素社会を実現する次世代パワーエレクトロニクスプロジェクト 窒化ガリウムパワーデバイスの実用化促進等に関する先導研究/新規結晶成長法の探索
公開日2016/11/25
報告書年度2015 - 2015
委託先名国立大学法人名古屋大学 国立研究開発法人産業技術総合研究所
プロジェクト番号P10022
部署名IoT推進部
和文要約
英文要約Title: The research of new growth method of GaN for power devices

GaN has the feature that its breakdown electric field is as high as 3.3MV/cm.
Therefore, it has been expected to realize the electric devices of high voltage region.
GaN crystal is usually grown by MOVPE system. But we confirmed high density of carbon
impurity. It compensate the n-type carrier, so we could not achieve the low density
n-type GaN which is needed to get high breakdown voltage devices. In this work, we
used HVPE system for GaN growth to eliminate the carbon impurity. The problems of
the HVPE growth are the surface flatness, Oxygen or Silicon impurity, controllability
of the growth rate and interface sharpness of hetero-structure. The aim of this study
is to confirm the realization of low impurity and improvement of the surface, and
to achieve the high breakdown voltage devices by HVPE system.
Experiment and results
We grew GaN on GaN/Sapphire template by HVPE. We used metal-Ga + HCl as III material
and NH3 as V material at N2 ambient. We change the HCl flow rate and control the V/III
ratio from 25 to 100 under growth temperature of 1045oC or 900 oC for GaN flatness or
impurity, respectively.
I.V/III ration dependence of GaN flatness(Nagoya Univ.)
In the case of V/IIIration of 100, we confirm the large step on the GaN surface grown
by HVPE. This is because the migration length is so long that Ga spicies was incorporate
at the around step edge. Therefore the much Ga could gather the step and made the
step bunching. On the centrally, we confirm the many pits on the surface of the sample
grown under V/III of 25. It is because the Ga migration is too short to coalesce the
initial island of GaN each other. In this study, we could get the smooth growth under
V/III ration of 50. The surface roughness is evaluated by AFM and we get the RMS value
of 0.7nm.
II.The impurity evaluation of HVPE-GaN layer by SIMS(Nagoya Univ.)
We evaluated the Oxygen, Hydrogen, Carbon and Silicon impurity by SIMS. The detection
limit is around 1016cm-3.The impurity density of Silicon and Carbon is less than 1016cm-3.
On the other hand,Oxygen and Hydrogen impurity level is as high as 5x1018cm-3,1x1018cm-3,
respectively. The origin of Oxygen is thought the decompose quartz chamber. We have
to change the material of chamber, growth condition to improve the Oxygen impurity.
It will be next issue.
III.Fabrication of diode or transistor(AIST)
In this year, we start up the simulation of device structure or measurements system
of the device feature by using oscilloscope
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