Emission spectrum control in monolithic blue-cyan dichromatic light-emitting diodes

InGaN-based dichromatic light emitting diodes (LEDs) emitting in the blue and cyan spectral ranges simultaneously, are investigated both experimentally and theoretically. Two main approaches to controlling the ratio of blue-to-cyan components in the emission spectrum are suggested and analyzed: (i) thickness variation of the GaN barrier between the blue and cyan quantum wells and (ii) optimization of the barrier doping with n- or p-type impurities. Detailed examination of the approaches is carried out in order to understand their capabilities for intentional variation of the blue-to-cyan ratio in a wide range. Based on numerical simulations, a novel mechanism, invoking enhanced Shockley-Read-Hall recombination in the barrier and underlying both approaches, is suggested and discussed. It is shown that proposed design of the monolithic blue-cyan LEDs does not result in substantial decrease of the LED emission efficiency compared to monochromatic blue or cyan reference samples.