Compound semiconductor lighting based on InGaN ultraviolet LED and ZnS phosphor system

White illumination characteristics of ZnS-based phosphor material excited by an In_xGa_1-xN-based single-quantum well (SQW) ultraviolet (W) light-emitting-diode (LED) have extensively been investigated. In order to obtain white luminescence, ZnS:Cu,Al, (Sr,Ca,Ba,Mg)₁₀(PO₄)₆Cl₂:Eu ²⁺ and Y₂O₂S:Eu³⁺ compounds were used. When a UV LED was operated at a current of 10 mA, chromaticity (x,y) color temperature (Tc) and general color rendering index (Ra) of the white luminescence were found to be (x,y)=(0.31, 0.34), Tc=6900 K and Ra=83, respectively. The value of chromaticity slightly changed with increasing forward current of the UV light source. As a result, it is possible to obtain stable white luminescence spectrum. The dependence of the luminescence brightness on the thickness of phosphor shows a tendency to saturate for reflection brightness, whilst for transmission brightness its dependence has a maximum peak due to light scattering effect. The reflection brightness was higher than the transmission brightness. It is shown that the white luminescence light of stable chromaticity and high brightness under the reflection condition can be obtained