Localization of carriers for indium-rich nanostructures incorporated in the MQWs is observed on nano-ELO and conventional GaN templates due to well width fluctuation and localized strain regions at the interface of the GaN barrier/GaN well.
A very small variation of PL peak energy over the wafer indicates InAs quantum well width fluctuation of only a fraction of a monolayer and hence extraordinary thickness accuracy, a conclusion further supported by high uniformity of both the emission intensity and PL linewidth.
During this period, DNA is rotated about 45° along with the groove width fluctuation.
In the samples with normal band structure, interband transitions were observed with wide line width due to quantum well width fluctuations.
It has been shown before [26, 27] and mentioned above that the emission wavelength of the discussed QW is very sensitive to the InAs thickness, whilst the GaInSb width fluctuations have a minor impact on the transition energy.
In two samples with normal band structure: wide (30 nm) HgCdTe QW and narrow (4.8 nm) HgTe QW, interband CR transitions have been revealed in the spectra, the interband absorption line width in the narrow QW being spread due to QW width fluctuations.
The competition relationship in a PL-integrated intensity of excitonic transitions reveals that the PL spectrum is sensitive to quantum-well-width fluctuation.
It was found that an average half monolayer well-width fluctuations are the dominant broadening mechanism of the excitonic line for QWs thinner than 10 nm.
For a typical blue MQW LED, exciton localization effect has been proposed to improve the IQE, which was related to several structural imperfections [10 13], such as compositional fluctuations of indium within InGaN wells [14, 15], formation of dot-like In-rich clusters [16 18] and well-width fluctuations in the activated layers [19], all of which were dependent on indium fractions in the wells.
On the one hand, the structural quality of the QW can be characterized by studying the inhomogeneous broadening generally induced by the well width (LW) fluctuation and alloy disorder.
As shown in Fig. 6, with applied field of 2.16, 2.42, 2.74, and 3.07 V/um, emission current of 53.1, 103.6, 203.6, and 400.3 uA could be achieved, and they remained almost constant during the 60-h continuous measurement, and the fluctuation width of the emission current for 60 h were all in ±5 %.
