AlInN系3元混晶の成長とInN/AlInN MQWs構造の作製評価(特別セッションテーマ: InNはどこまでよくなったか?, 窒化物半導体光・電子デバイス・材料, 及び関連技術, 及び一般(窒化物半導体国際ワークショップ))  [in Japanese] Growth and Characterization of AlInN Ternary Alloys and InN/AlInN MQWs  [in Japanese]

InNを中心とした窒化物半導体は光通信波長帯での新しい光デバイス材料として期待される。我々は、InNを井戸層とした多重量子井戸(MQWs)構造を作製する際に、InNとの格子不整合度をInGaN系3元混晶と比べ小さくでき、かつ大きなバンドオフセットを期待できるAlInN系3元混晶をバリア層として用いることを検討した。はじめに、AlInN系3元混晶のエピタキシやその特性を把握するため、全組成範囲でのAlInNの成長を行い、その結晶性や光学特性を評価した。成長温度はAlInNの組成および組成不均一性、結晶性に大きく影響することが分かった。また、AlInNのボーイングパラメータは約4.78eVであることが見積もられた。さらに、Al組成30%程度のAlInNバリア層を用いてInN/AlInN MQWs構造を作製した。x線回折測定により3次までのサテライトピークを、低温フォトルミネセンス測定において0.68から0.99eVまでのInN井戸層からの発光ピークを観察した。これらの結果はAlInN系3元混晶とこれらを用いたMQWs構造がInN系窒化物半導体の光通信波長域の光デバイス材料として有望であることを示している。

InN has been paid much attention as a potentially promising material for new-functionality photonic devices operating in optical communication wavelengths, because its energy bandgap has been found such small as 0.64eV, and is not 1.9eV any more, recently, For the InN-based multi quantum well (MQWs) using the InN and/or In-rich ternary alloys as the well, we have proposed to use AlInN ternary alloys as the barrier layer. Because compared to the case when using InGaN ternary alloys as the barrier layer, the lattice mismatch between the well and barrier can be decreased with keeping the conduction band offset large. First, we grew AlInN ternary alloys in the whole composition range by RF-MBE and investigated their crystalline and optical properties. It was estimated that the bowing parameter of AlInN ternary alloys was about 4.78eV. Then we fabricated the MQWs consisting of the InN well and the AlInN barrier layer with 〜30% Al composition. We found that the growth temperature greatly affected the composition and crystallinity of AlInN ternary alloys. By optimizing the growth conditions, we for the first time successfully fabricated the InN-based MQWs with Al_xIn_<1-x>N (〜0.2<x<〜0.3) barrier layers. Clear XRD satellite peaks up to the 3^<rd> order were observed. Further the photoluminescence peaks ranging from 0.68 to 0.99eV were observed depending on the well. These results indicate that fine periodic InN-based MQWs-structures with fairly flat and sharp interfaces were obtained. We think that the AlInN ternary alloys and InN/AlInN MQWs are potentially applicable for new-functionality photonic devices operating in the optical communication wavelength.