Observations of two-dimensional electron gases in AlGaN/GaN high-electron-mobility transistors using up-converted...

Up-converted photoluminescence excitation (UPLE) spectra of AlGaN/GaN high-electron-mobility transistors (HEMTs) grown on Si substrates have been investigated. Based on the temperature dependence of UPLE, the 3.335-eV excitation peak is attributed to the two-dimensional electron gases (2DEGs) in the AlGaN/GaN heterostructure. A two-step two-photon absorption process through real intermediate quantum-well states is suggested to be responsible for the up-converted luminescence in the AlGaN/GaN HEMTs.