| 研究概要 |
2層積層法を用いてGaAs基板上InAs量子ドットの発光長波長化を目指した。発光長波長化には、下層QDの密度とサイズ制御、ならびに上層QDの歪緩和制御が重要であり、これらを最適化して波長約1.4ミクロンまでの長波長化に成功した。歪み補償に必要不可欠な希釈窒化GaAs成長条件の最適化及びその物性解明を目的にGaNAs/AlGaAs構造の作製に関する研究を行った。成長中断を導入して窒素濃度を高精度で制御する手法を開発した。作製した構造は良好な発光特性を示し、高品質性であることが分かった。一方で、高濃度窒素添加GaNAs成長時には3次元島状成長が起こることが分かった。
Extensions of emission wavelength of InAs/GaAs QDs by using bi-layer QD growth have been investigated. The extension has been found with an enlargement of the upper layer (active) QDs occurred by optimizing several growth parameters: growth temperature of lower (seed) QDs, amount of InAs supplied for seed- and active-QDs. These optimized parameters lowered the density of the seed-QDs strain spreading upward, which resulted in an enlargement of the active-QDs. We achieved a control of the extension of emission wavelength up to approximately 1.4μm. We also studied the growth of GaNAs/AlGaAs heterostructures on GaAs (100) substrates by plasma-assisted molecular beam epitaxy. By introducing periodic growth interruption and nitrogen (N) supply to the interrupted surfaces during the growth of GaNAs, we achieved high controllability of the average N concentration in GaNAs layers. We observed three-dimensional island growth of GaNAs on the N-rich surfaces.
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