ZnSe MIS二极管蓝色电致发光的空间分布

本文研究了用ZnS多晶薄膜作绝缘层时制备的ZnSe MIS二极管,在正向电压激发下的蓝色电致发光的空间分布,在光学显微镜下观察到电致发光呈稀疏的点状分布。为了了解发光点的起因,用扫描电镜观测了二极管的二次电子像(SEI),束感生电流像(EBICI)和吸收电流像(AEI)。一个重要的发现是二极管的电致发光点(ELS)和EBICI有相当好的对应关系。文中指出了发光点的存在与绝缘层(Ⅰ)的引入有关。绝缘层一半导体(I-S)界面较大的能带失配和较差的结合,从而产生较多的无辐射复合中心,是产生稀疏发光点可能的原因。文中根据对发光点起因的分析,提出用ZnSe多晶薄膜取代ZnS多晶薄膜作绝缘层来铡备ZnSe MIS二极管。当用显微镜观察时,电致发光点呈密集分布,而用肉眼观察时是均匀的蓝色发光。文中还指出了进一步改进电致发光空间分布的可能途径。

SPATIAL DISTRIBUTION OF BLUE ELECTROLUMINESCENCE IN ZnSe MIS DIODES

In recent years there has been considerable interest in blue EL emitted by forward-biased ZnSe MIS diodes1-5]. In our earlier work 6,7], attention was directed to determining the origin of two emission bands in the blue at 4655 and 4770 Å at room temperature. In the present paper the main interest is focused on the spatial distribution of blue EL in ZnSe MIS diodes.Nominally undoped ZnSe crystal, grown in this laboratory, were used in the present experiments. The boule crystals were grown from the vapour phase in sealed capsules containing slight excess of zinc 8,9]. Dice with dimensions of 3×3×1 mm3 were cut from the boules, and annealed in molten zinc at 850℃ for 100 h to reduce their resistivities to the range 1-10Ωcm. After polishing and etching, one large area face of the dice was then provided with an indium ohmic contact. A thick (500-1000 Å) layer of ZnS was deposited on the opposite face by electron beam, and finally a circular gold electrode 1 mm in diameter was evaporated on top of ZnS layer.The photo of EL spots was taken from the surface of the dice carrying the gold contact with Model XJL-01 optical microscope. Model HHS-2X scanning electron microscope has been used to study the ZnSe diodes.