Physical Properties control of II-VI Compound Semiconductors for Blue Light-Emitting-Devices

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Of the II-VI compounds, ZnSe and ZnS have the greatest potential for use in blue light-emitting-diodes. For device applications, it is important to control both conductive type and resistivity of these materials. We have investigated growth of acceptor doped ZnSe and donor doped ZnS films by Metalorganic Chemical Vapor Deposition (MOCVD), and obtained several important results as follows;1. Acceptor doping to ZnSe: We have examined the growth of p-type ZnSe films by using nitrogen (N) and lithium (Li) as acceptor impurtites. First, growth of N-doped ZnSe films by using NH_3 as a dopant has been carried out.It has been shown that the njtrogen atoms act as shallow acceptors in ZnSe through low-temperature photoluminescence measurements, byt some deep centers related to the nitrogen impurity are also introduced into highly N-doped films. In case of the growth of Li-doped ZnSe, cyclopentadienly Li was used as a dopant. Up until now, it has been said that Li is an amphoteric impurity in ZnSe. However, it was found that the lithium atoms incorporated into the ZnSe films act as shallow acceptors through the photoluminescence properties. Furthermore, it was also found that the intensities from deep centers related to Zn-vacancy are remarkably reduced in Li-doped ZnSe.2. Donor doping to ZnS: Growth and properties of donor doped ZnS films by MOCVD have been investigated. Trimethylaluminum and HCl were used as donor dopant sources. Both Al- and Cl- doped ZnS films with resistivity as low as about 1 .cm can be grown. Furthermore, an excitonic emission related to a shallow donor level and emission from self-activated centers are dominant peaks in the low-temperature photoluminescence spectrum.