Size-dependent light output, spectral shift, and self-heating of 400 nm InGaN light-emitting diodes

Abstract

We have systematically investigated the impact of device size scaling on the light output, spectral shift, and self-heating of 400 nm InGaN light-emitting diodes (LEDs). Devices with diameters in the range 20–300 μm have been studied. It is shown that smaller LED pixels can deliver higher power densities (despite the lower absolute output powers) and sustain higher current densities. Investigations of the electroluminescence characteristics of differently sized pixels against current density reveal that the spectral shift is dominated by blueshift at the low current density level and then by redshift at the high current density level, owing to the competition between the bandgap shrinkage caused by self-heating and band-filling effects. The redshift of the emission wavelength with increasing current density is much faster and larger for the bigger pixels, suggesting that the self-heating effect is also size dependent. This is further confirmed by the junction-temperature rise measured by the established spectral shift method. It is shown that the junction-temperature rise in smaller pixels is slower, which in turn explains why the smaller redshift of the emission wavelength with current density is present in smaller pixels. The measured size-dependent junction temperature is in reasonable agreement with finite element method simulation results.

On the Effect of Step-Doped Quantum Barriers in InGaN/GaN Light Emitting Diodes

“…Meanwhile, Devices II and III show a shorter peak emission wavelength compared to Device I, which is attributed to the slightly relieved QCSE by Si-doped quantum barriers [29]. However, the less pronounced blue-shift for all the three devices as the injection current increases is caused by the junction heating effect [38].…”

Strain relaxation in InGaN/GaN micro-pillars evidenced by high resolution cathodoluminescence hyperspectral imaging

“…These arrays had a pitch chosen to give a fill factor of 26%, corresponding to the average value for the repeating unit in the arrays of fabricated pillars. 24 The strain distribution calculated for the middle pillar was used to estimate the spectral shifts. The in-plane strain isotropy for the (0001) growth orientation allowed the simulation to be simplified to a two-dimensional case.…”

“…The micro-pillars were fabricated with diameters ranging from 2 to 150 lm in a configuration described previously. 24 The top p-GaN layer was firstly thinned down to 40 nm by inductively coupled plasma (ICP) etching. This step facilitated CL measurements with high lateral resolution by reducing the accelerating voltages needed to excite QW emission.…”

Visible light communication using InGaN optical sources with AlInGaP nanomembrane down-converters

“…1(b)]. The micro-LED chip, with peak emission at 450 nm, is fabricated using a commercial p-i-n GaN structure grown on c-plane sapphire, following the procedure reported in [14]. The chip is made of 8 micro-LED pixels of 4 different sizes, 50 x 50 μm 2 , 75 x 75 μm 2 , 100 x 100 μm 2 and 150 x 150 μm 2 .…”