One quarter million (500×500)pixel arrays of silicon microcavity plasma devices: Luminous efficacy above 6lumens∕watt with Ne/50% Xe mixtures and a green phosphor

Abstract

Arrays comprising 250 000 Si microcavity plasma devices, each with an emitting aperture of 50×50μm2 and tapered sidewalls (inverted pyramid cavity), have been fabricated in 100-mm (4″) diam. wafers and operated in the rare gases and Ar∕N2 mixtures with sinusoidal ac or bipolar dc excitation. Having an overall active area of 25cm2 and a 25% filling factor, these 500×500 arrays exhibit the pixel-to-pixel emission uniformity characteristics of arrays at least a factor of 6 smaller, and yet are efficient in generating vacuum ultraviolet (VUV) radiation. Luminous efficacies above 6lm∕W and luminance values approaching 2000cd∕m2 are measured when a 500×500 array, operating with a Ne/50% Xe gas mixture, illuminates a 20-μm-thick film of a commercial green phosphor (Mn:Zn2SiO4). Despite the nonoptimal transmission geometry of the array-phosphor structure, the efficacy and luminance produced by the VUV-driven phosphor for a Ne/50% Xe mixture and a total pressure of 800Torr are measured to be 7.2±0.6lm∕Watt and 525±75cd∕m2, respectively, for a 20-kHz sinusoidal ac voltage of ∼284V rms. Maximizing the luminous efficacy–luminance product lowers the optimal pressure of Ne/50% Xe mixtures to roughly 1atm. The magnitude of the radiant output generated by these arrays, in addition to the rapid rise in emitting efficiency with increased Xe content in Ne/10%–50% Xe mixtures, suggest that this microplasma array structure will be of value for both microdisplay and biomedical applications.