Researchers unveil optoelectronic ICs breakthrough
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Researchers have a announced a project to develop optoelectronic integrated circuits – silicon and nitride LEDs integrated onto a single chip for one bit digital counters.The research is being undertaken by Akihiro Wakahara, pictured, and colleagues from Toyohashi University of Technology.
The study looks to address the issue of silicon having an indirect band gap. This severely limits its use for fabricating photonic devices such as LEDs and lasers. The new solution is built around integrating silicon devices with LEDs produced using direct band gap compound semiconductors, in the form of optoelectronic integrated circuits (OEICs). The team says it has now demonstrated the first one bit counter circuit OEIC with an optical output consisting of silicon field effect transistors integrated with gallium phosphide nitride (GaPN) LEDs on a single chip.
The monolithic ICs were fabricated using lattice matched Si/GaPN/Si heterostructures grown on silicon substrates in a dual chamber molecular beam epitaxy (mbe) system. According to the researchers, growth of the silicon capping layer at a high temperature of 850? led to a dramatic reduction of the threshold voltage to -2.1V and an increase of the channel mobility of the p-mosfet to 82 cm2Vs. This improvement is attributed to a decrease in phosphorus incorporation during the growth of the capping layer.
The one bit counter circuit fabricated using the n-Si/p-GaPN/n-GaPN/GaP/n-Si heterostructure exhibited normal operation, where red light emission from the input and output indicators was in synchronisation with the input and output logical voltages.
