Abstract
The electroluminescence (EL) properties of InGaN/AlGaN ultraviolet light-emitting multiple quantum wells (MQWs) with identical average In content but different In gradients (In content increases linearly, along the growth direction) are investigated numerically. It is found that the luminescence efficiency is improved, and the EL spectral peak wavelength becomes longer for the MQW sample with a larger In gradient. Since the influence of In gradient is different for the conduction and valence bands in InGaN layers, the distribution of electrons and holes in QWs may be changed, leading to a redshift of EL spectra. In particular, when the In gradient increases, the overlap integral of electron-hole wavefunction in InGaN QWs increases, resulting in a higher radiative recombination rate and an enhanced EL intensity.
Highlights
Group-III nitrides (AlN, GaN, and InN) and their ternary and quaternary alloy materials have attracted lots of research interest in the field of semiconductor optoelectronic materials because of the wide and tunable direct band-gap structures covering the spectral range from ultraviolet (UV) to infrared [1,2,3]
light-emitting diodes (LEDs) to increase the height of potential barriers and enhance the ability to capture and confine carriers in the multiple quantum wells (MQWs) active region, leading to a reduced leakage current, as well as an enhanced device performance of UV LEDs [7]
It is found that the peak wavelengths of EL spectrum increase from samples A to D, i.e., the sample’s EL spectrum redshifts with increasing In increase from samples A to D, i.e., the sample’s EL spectrum redshifts with increasing In gradient
Summary
Group-III nitrides (AlN, GaN, and InN) and their ternary and quaternary alloy materials have attracted lots of research interest in the field of semiconductor optoelectronic materials because of the wide and tunable direct band-gap structures covering the spectral range from ultraviolet (UV) to infrared [1,2,3]. LEDs to increase the height of potential barriers and enhance the ability to capture and confine carriers in the MQW active region, leading to a reduced leakage current, as well as an enhanced device performance of UV LEDs [7]. MQW layers, the strong lattice mismatch may generate a large number of polarization charges at the InGaN/AlGaN interfaces due to the piezoelectric polarization effect, which enhances the polarization-induced electric field in InGaN QWs and leads to a stronger quantum-confined Stark effect (QCSE) [10,11]. It was found that when the In content gradually increases along the epitaxial growth direction in InGaN well layers, QCSE may be weakened and luminescence efficiency can be improved significantly [17,18,19,20,21,22]. In content in InGaN QWs and will be discussed in detail later
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