Power dependence of unusual bands in photoluminescence spectra of AlGaN/GaN heterostructures

Abstract

AbstractAlGaN/GaN heterostructures with a two‐dimensional electron gas (2DEG) grown by metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) techniques were investigated by photoluminescence (PL) spectroscopy. Series of PL bands located below the donor bound excitons band have been observed for a high quality MOCVD sample. Two of these PL bands peaked at ħωmax=3.446 and ħωmax=3.423 eV have been observed at both continuous and pulse excitation and connected with the recombination of 2DEG localized at the first and the second levels in the quantum well with free holes. The PL band at ħωmax=3.36 eV may be attributed to recombination of the 2DEG electrons with holes located at acceptors. Band at ħωmax=3.41 eV is not connected with 2DEG because of this band didn’t disappear after etching of the AlGaN layer and this band was observed in all samples. An intensity of all these four PL bands increased superlinearly with rise of the excitation power. The exponents for the Y bands more than 2, while the exponent for the excitonic band is about 1.5 at T=5 K. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)