Abstract
Carrier transport issues in a (11–22) semi-polar GaN based white light emitting diode (consisting of yellow and blue emissions) have been investigated by detailed simulations, demonstrating that the growth order of yellow and blue InGaN quantum wells plays a critically important role in achieving white emission. The growth order needs to be yellow InGaN quantum wells first and then a blue InGaN quantum well after the growth of n-type GaN. The fundamental reason is due to the poor hole concentration distribution across the whole InGaN quantum well region. In order to effectively capture holes in both the yellow InGaN quantum wells and the blue InGaN quantum well, a thin GaN spacer has been introduced prior to the blue InGaN quantum well. The detailed simulations of the band diagram and the hole concentration distribution across the yellow and the blue quantum wells have been conducted, showing that the thin GaN spacer can effectively balance the hole concentration between the yellow and the blue InGaN quantum wells, eventually determining their relative intensity between the yellow and the blue emissions. Based on this simulation, we have demonstrated a monolithically multi-colour LED grown on our high quality semi-polar (11–22) GaN templates.
Highlights
General illumination is one of the major sources for electricity demand globally
Sizov et al.27 observed severe non-uniform carrier distribution among the InGaN multiple quantum wells (MQWs) of a laser diode grown on a c-plane substrate, leading to an increase in threshold current when the number of InGaN MQWs is above 2, while they did not observe this phenomenon on the LDs grown on semi-polar substrates
The results indicate that the hole transportation issue is vitally important for designing a dual emission light-emitting diodes (LEDs)
Summary
Carrier transport issues in a [11,12,13,14,15,16,17,18,19,20,21,22] semi-polar GaN based white light emitting diode (consisting of yellow and blue emissions) have been investigated by detailed simulations, demonstrating that the growth order of yellow and blue InGaN quantum wells plays a critically important role in achieving white emission. In order to capture the holes in both the yellow InGaN quantum wells and the blue InGaN quantum well, a thin GaN spacer is required prior to the blue InGaN SQW in order to effectively balance the carrier concentration between the yellow InGaN quantum wells and the blue InGaN quantum well, which eventually determine their relative intensity between yellow and blue emission Based on this simulation, we have demonstrated a monolithically multi-colour LED grown on our high quality semi-polar [11,12,13,14,15,16,17,18,19,20,21,22] GaN templates
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