气相法によるznse 单结晶成长とその应用.pdfVIP

特別論文 気相法による Z n S e 単結晶成長とその応用 並　川　靖　生 ZnSe Single Crystals Grown by Vapor Growth Methods and Their Application ─by Yasuo Namikawa ─ZnSe based white LED can be fabricated by homoepitaxial growth on ZnSe conductive substrate. This LED emits white light by mixing the blue − green emission from the ZnCdSe active layer and the deep level yellow emission from the ZnSe substrate excited by the active layer emission. Large conductive ZnSe substrates with high quality are required for this device application. The vapor growth techniques, such as PVT (physical vapor transport) method and CVT (chemical vapor transport) method, were applied to grow ZnSe single crystals. The most important problem to be solved in PVT growth of ZnSe single crystal is voids formation during the crystal growth. The voids formation was eliminated by the semi − open free − growth method in which the growing crystal could be kept at the local minimum temperature position during the crystal growth. ZnSe single crystals of 45 mm diameter and 35 mm length with dislocation density of about 5 x 103 cm-2 could be grown by this PVT method. On the other hand, the suppression of the influence of the convection during the crystal growth is the problem for CVT method. This subject was solved by the rotational CVT method. ZnSe based white LED could be operated at the low applied voltage of 2.75 V and demonstrated an optical output power of 4.25 mW at a forward current of 20 mA. The life time of the LED showed longer than 10,000 hours at room temperature operation. This paper reviews mainly ZnSe single crystal growth techniques and shows some application results. Keywords: ZnSe, crystal growth, PVT, CVT, white LED 1.　緒　　言 ZnSe（セレン化亜鉛）は約 2.58 eV のバンドギャップ 導電性とすることが必要である。青色発光素子開発の中で、 エネルギーを持つII-VI 族化合物半導体であり、その