Technical Insight
Diamond pn junction emits UV light (Nitride News)
Researchers at the National Institute for Materials Science in Tsukuba, Japan, have reported UV emission from a pn junction formed from boron-doped (p-type) and phosphorus-doped (n-type) diamond (S Koizumi et al. Science 2001 292(8) 1889). The layers were grown epitaxially on 2 mm2 single-crystal diamond substrates by microwave-plasma-enhanced CVD. A strong UV emission peak at 235 nm, attributed to free exciton recombination, was observed when the forward bias voltage reached 20 V. This was accompanied by broadband visible emission, attributed to the poor crystalline quality of the boron-doped layer. By improving the quality of this layer, the broadband emission can be suppressed, making a diamond LED emitting monchromatically at 235 nm feasible.