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Variation with Al alloy composition in AlGaN

For bulk AlGaN the bandgap variation is accurately reflected in the PL spectrum, however it is not true for AlGaN/GaN heterostructures where due to the strong electric field there is a red shift. So Al composition calculated from PL peak position is NOT totally accurate.

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Variation with Al alloy composition in AlGaN

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  1. For bulk AlGaN the bandgap variation is accurately reflected in the PL spectrum, however it is not true for AlGaN/GaN heterostructures where due to the strong electric field there is a red shift. So Al composition calculated from PL peak position is NOT totally accurate Variation with Al alloy composition in AlGaN

  2. The e1-h1 transition is most probable and observed with highest intensity At higher temperature other transitions are also observed All peaks are red-shifted at higher temperatures PL spectra of Quantum Wells n = 3 n = 2 n = 1 n = 1 n = 2 n = 3

  3. With increasing well width The intensity increases due to increased confinement The peak position shifts to lower energy due to reduction in quantum size effect (QSE) i.e. splitting of energy levels in a QW The full width at half maximum (FWHM)  also decreases PL spectrum for non-polar QW

  4. With increase in well thickness Intensity decreases due to reduced overlap of the electron and hole wavefunctions due to polarization Energy decreases due to Quantum Confined Stark Effect (QCSE) or reduction in transition energy gap due to electric field Polar (Nitride) QW PL spectrum Electron and hole wave-functions for non-polar material Electron and hole wave-functions for polar material due to built-in electric field

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