Strong near-ultraviolet and blue emissions at room temperature from two-step grown In-rich InGaN/GaN multiple quantum wells

Strong near-ultraviolet (similar to 400 nm) and blue (similar to 450 nm) emissions were obtained at room temperature from a 1 nm-thick In-rich InGaN/GaN multiple quantumwell (MQW) structure by introducing a two-step growth method in an InGaN quantum well layer. The excitation power-dependent and temperature-dependent photoluminescence and high-resolution transmission electron microscopy revealed the 400 nm peak to be the result of a band-to-band transition in 1 nm-thick InGaN MQW, whereas the 450 nm peak was attributed to localised centres induced by the second step in InN growth and growth interruption. The thermal stability of the 450 nm peak was much better than that of the 400 nm peak, strongly suggesting that the ultrathin In-rich InGaN MQW layer grown by the two-step growth method can be an active layer for high-efficiency visible light sources.