Low Pressure Vapor Phase Growth and Control of Electrical and Optical Properties of Zinc Selenide Single Crystalline Thin Films

采用低压气相外延（LPVPE）技术在GaAs衬底上生长了硒化锌（ZnSe）单晶薄膜<-6><-1>。在外延生长前对衬底表面进行氢射频等离子体清洗，获得了高重复性的生长实验。通过精确控制生长过程中的VI/II比值，生长出了高纯度的未掺杂ZnSe层，其低温光致发光光谱以自由激子发光为主，在0.1Torr下生长的未掺杂ZnSe层具有高的发光系数。通过In掺杂提高了载流子浓度，并将其控制在10^<16>-10 ^<18>cm-3范围内<-3>。当生长压力为10 μ Torr时<-4>，未掺杂层显示出几cm的低折射率。层电阻率的生长压力依赖性表明，补偿残余浅施主的深能级密度随生长压力而变化。室温载流子浓度为5x 10 ^ cm^2的2n掺杂层<15><-3>的低温电子迁移率高于800 cm^2/v. sec。高迁移率表明残留杂质的密度低。当向生长室中通入NH_3气体时，在2.793 eV处观察到一条新的发光线，该发光线是由束缚在浅受主上的激子复合引起的，其强度随NH_3气体浓度的增加而增强。受主束缚激子发射强度随VI/II比值的增加而降低，确定了该发射是由于Se位上的N受主引起的。

Single crystalline thin films of zinc selenide (ZnSe) have been grown on GaAs substrates by using low pressure vapor phase epitaxy (LPVPE) technique, in which zinc and selenium vapors are supplied into hydrogen atmosphere with pressure of 10^<-6>-10^<-1> Torr. A high reproducibility in growth experiment was attained by utlizing the hydrogen RF plasma cleaning of substrate surface just before the epitaxial growth. The VI/II ratio during the growth was precisely controlled and high-purity undoped ZnSe layers, which exhibit low-temperature photoluminescence spectra dominated by the free exciton emission, were grown.Undoped ZnSe layers grown at 0.1 Torr were of high resistivities. The carrier concentration was increased by In doping and controlled in the range of 10^<16>-10^<18> cm^<-3>. When the growth pressure was 10^<-4> Torr, undoped layers showed low resistivities of several .cm. The growth pressure dependence of the layer resistivity indicates that the density of deep levels compensating the residual shallow donors varies with the growth pressure. An 2n-doped layer with room-temperature carrier concentration of 5x10^<15> cm^<-3> had a low-temperature electron mobility higher than 800 cm^2/v.sec. The high mobility indicates low densities of residual impurities. When NH_3 gas was introduced into the growth chamber, a new emission line due to recombination of excition bound to a shallow acceptor was observed at 2.793 eV, and the emission increased in intensity as the concentration of NH_3 was increased. The acceptor bound exciton emission intersity decreased with increasing the VI/II ratio, which ascertained that the emission was due to N acceptor at Se site.