Toyoyasu Tadokoro

Cathodoluminescence image of defects and luminescence centers in ZnS/GaAs(100)

The spatial distributions of the cathodoluminescence (CL) emissions from thin ZnS films on GaAs(100) have been examined by the low‐temperature CL measurement system combined with a transmission electron microscope (TEM). The correlation between these CL emissions and structural defects were studied by comparing the monochromatic CL images with the TEM images for both plan‐view and cross‐sectional observations. It is found that the neutral acceptor–bound exciton associated emission (A0,X) and the free‐electron‐to‐ionized acceptor transition emission (e,A) are affected by the stacking fault distribution. The localization of the emission due to the deep‐level emission transition near the interface suggest the diffusion of Ga atoms from the GaAs substrate. The characteristic distributions of the CL emission regions can be explained by considering the competitions among the recombination channels of those radiative processes for each type of an excess carrier, an electron, or a hole.

Correlation between cathodoluminescence and structural defects inZnS/GaAs(100) andZnS/eGaAs(100) studied by transmission electron microscopy

The spatial distributions of the cathodoluminescence (CL) emissions from thin ZnS and ZnSe films on GaAs(100) have been examined by the low-temperature CL imaging system combined with a transmission electron microscope (TEM). The correlation between these CL emissions and structural defects were studied by comparing the monochromatic CL images with TEM images for both plan-view and cross-sectional observations. It is found that the bound exciton associated emission (A0, X) and the (e, A) emission are affected by the stacking fault distribution. The localization of the emission due to the DLE transition near the interface suggest the diffusion of Ga or As atoms from the GaAs substrate.

Effects of Mn effusion cell temperature on the film properties and on the AC electroluminescence of molecular beam deposited ZnS:Mn

Abstract The AC thin-film electroluminescent (ACTFEL) devices were prepared by using 1 μm-thick ZnS:Mn luminescent layers formed by molecular beam deposition (MBD). The devices had a structure of glass/In2O3/barium-titanate/ZnS:Mn/Al. The EL properties of the device are remarkably dependent on the temperature of a Mn effusion cell (TMn) during the ZnS:Mn deposition. Although the crystalline quality of the layers was poor and the surface morphology was rough, a low threshold field (Eth) of 0.82×106 V/cm, and a high maximum luminance (Lmax) of 4200 cd/m2 were obtained at 5 kHz sinusoidal operation. The ACEL properties were dependent not only on the crystallographic quality but also on the Mn concentration in the luminescent layer.

Low-voltage-driven a.c. thin film electroluminescent cell containing a ZnS:Mn film deposited by molecular beam epitaxy

Abstract The glass/In2O3:Sn/BaTiO3/ZnS:Mn/HfO2/SiO2/HfO2/Al a.c. thin film electroluminescent (EL) device was fabricated. The ZnS:Mn luminescent film of 4000 A thickness was deposited by molecular beam epitaxy (MBE). The crystalline quality of the film was worse than that of the ZnS:Mn prepared by vacuum deposition (VD) because the deposition conditions were unoptimized. Even though the MBE ZnS:Mn film had a poor crystalline quality, the EL properties were superior to those of a VD film. The threshold voltage and the maximum brightness of an MBE EL cell were 56.5 V (r.m.s.) and 2500 cd m-2 respectively, at 5 kHz sinusoidal operation. It was suggested that these improved EL properties are due to more effective incorporation of mangenese light-emitting centres into ZnS.