Comparative Study on Nonradiative Recombination Centers in Proton Irradiated InAs/GaAs Quantum Dot Structure by Two Wavelength Excited Photoluminescence

Comparative study on nonradiative recombination (NRR) centers in InAs/GaAs quantum dot (QD) structure generated by 3 MeV proton irradiation is performed by two wavelength excited photoluminescence (TWEPL). The above-gap excitation (AGE) source of 2.33 eV or 1.26 eV is used to excite GaAs host material or InAs QDs, respectively. The QD PL intensity decreased after irradiation of below-gap excitation (BGE) of 0.75 eV over AGE, indicating a pair of NRR centers activated. The proton irradiation at fluence of
$7\times 10^{11}\mathrm{cm}^{-2}$
reduces the NRR density, while that of
${4\times 10^{12}\mathrm{cm}^{-2}}$
increases it. Defect formation, carrier injection and their fluence dependence explain experimental results.