Analysis of localization effect in blue-violet light emitting InGaN/GaN multiple quantum wells with different well widths

Abstract

Four blue-violet light emitting InGaN/GaN multiple quantum well (MQW) structures with different well widths are grown by metal-organic chemical vapor deposition. The carrier localization effect in these samples is investigated mainly by temperature-dependent photoluminescence measurements. It is found that the localization effect is enhanced as the well width increases from 1.8 nm to 3.6 nm in our experiments. The temperature induced PL peak blueshift and linewidth variation increase with increasing well width, implying that a greater amplitude of potential fluctuation as well as more localization states exist in wider wells. In addition, it is noted that the broadening of the PL spectra always occurs mainly on the low-energy side of the PL spectra due to the temperature-induced band-gap shrinkage, while in the case of the widest well, a large extension of the spectral curve also occurs in the high energy sides due to the existence of more shallow localized centers.

Physical implications of activation energy derived from temperature dependent photoluminescence of InGaN-based materials

“…[15] The S-shaped temperature dependence of peak energy is evidence of the presence of localized states in the InGaN wells. [16,17] On the other hand, it can be seen from Figs. 2(a) and 2(c) that strong thermal decay of peak intensity for GaN starts at about 20 K, a temperature considerably lower than that for the InGaN/GaN MQW (75 K).…”

Performance Improvement of GaN Based Laser Diode Using Pd/Ni/Au Metallization Ohmic Contact

“…The n-type and p-type doping precursors are silane (SiH 4 ) and dicyclopentadienyl magnesium (Cp 2 Mg), respectively. For detailed epitaxial growth processes, please refer to reference [38]. The common epitaxial structure of the GaN based laser diode is shown in Figure 1, which consists of a 2 µm thick GaN buffer layer, a 1 µm thick n-AlGaN confinement layer, a 100 nm GaN lower waveguide layer, two pairs of InGaN/GaN quantum well structures as the active region, a 100 nm p-GaN upper waveguide layer, a 20 nm p-AlGaN electron blocking layer, a 600 nm thick p-AlGaN confinement layer, and a 80 nm thick p-GaN contact layer with Mg concentration of 1 × 10 19 cm −3 .…”

Monolithic semi-polar ( 1 1 ¯ 01 ) InGaN/GaN near white light-emitting diodes on micro-striped Si (100) substrate*

“…[1][2][3][4][5] By reducing the indium content, the band gap of InGaN increases from 0.7 eV to 3.4 eV, which corresponds to the wavelength of emission from ultraviolet to infrared. [6][7][8] Traditionally, polar blue InGaNbased LEDs are combined with phosphors to produce white LEDs [9][10][11][12] This method has achieved a high lumen efficiency (197.8 lm/W), [13] but this method is not a fully meaningful LEDs lighting technology, and there are still some shortcomings: the process is complex, [14] conversion efficiency is still far from the theoretical efficiency limit (298.7 lm/W), [13] and polar InGaN has a strong quantum confined stark effect (QCSE). [15] As a result, researchers are looking for a new method to produce white LEDs on a monochromatic chip with no phosphors.…”