PL AND SIMS OF VAPOR-PHASE EPITAXIAL ZNSE FILMS

Photoluminescence and impurity distributions were investigated on ZnSe films. The ZnSe films were grown at 350-degrees-C by conventional VPE on (100)GaAs and on p-type ZnSe-film-on-GaAs substrates. Etching in an HCl gas flow at the growth temperature for 5 min was carried out just before the films were grown. Their SIMS profile revealed that the films were doped unintentionally with a high concentration of Ga from the rear surface of the GaAs substrate due to the residual HCl gas. The film grown on GaAs was conductive and its electron concentration was on the order of 10(17) cm-3 due to Ga donors. The diode structure could not maintain a sufficient current since the Ga donors in the top layer were compensated by Li(Zn) and/or V(Zn). The Li concentration in the top layer was on the order of 10(15) cm-3, while 10(16)-10(19) cm-3 of Li were detected between the free surface and a point 1-mu-m deep in a 5 min diffusion experiment performed at 250-degrees-C. The p-type film obtained with co-doping of Li and P seemed to inhibit out-diffusion of Li. The diffusion coefficient of Li at 250-degrees-C was 1.5 x 10(-12) cm2/s.