| Autor: |
Shukla, Nidhi, Rudra, Sourav, Karanje, Renuka, Mukhopadhyay, Debmalya, Das, Prasanna, Biswas, Bidesh, Baral, Madhusmita, Gupta, Mukul, Saha, Bivas |
| Zdroj: |
Chemistry of Materials; June 2024, Vol. 36 Issue: 11 p5563-5573, 11p |
| Abstrakt: |
Excitons are the lowest excited state of the electronic subsystem in semiconductors, composed of a bound electron–hole pair interacting via screened coulomb potential. Compared to the band-to-band transitions, excitons exhibit stronger luminescence with greater oscillator strength at low temperatures. However, achieving room-temperature excitonic luminescence in semiconductors is challenging due to their low binding energies. Magnesium nitride (Mg3N2), an emerging II-nitride semiconductor, hosts a room-temperature excitonic luminescence in the visible spectral range in the powder phase. Here, we show conclusive experimental evidence of strain-induced valence band splitting in epitaxial and stoichiometric Mg3N2thin films that leads to excitonic luminescence above and below its direct bandgap at room temperature. Growth-induced biaxial tensile strain splits the light hole and split-off hole bands in Mg3N2by ∼170 meV, which causes the above-bandgap luminescence. Optical absorption, synchrotron radiation ultraviolet photoemission spectroscopy, and photoluminescence measurements also confirm that Mg3N2is a direct bandgap semiconductor with an exciton binding energy of ∼40 meV. First-principles calculations with Heyd–Scuseria–Ernzerhof hybrid-functional support the strain-induced valence band splitting and above-bandgap excitonic feature. Room-temperature multiple exciton luminescence in Mg3N2would be useful for visible-light-emitting diodes (LEDs), semiconductor lasers, and other optoelectronic applications. |
| Databáze: |
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