OPTICAL STUDIES OF GAINP(ORDERED) GAAS AND GAINP(ORDERED)/GAP/GAAS HETEROSTRUCTURES/

We report on a detailed optical study of emission from a series of GaI nP (ordered)/GaAs heterostructures. Some of these structures contain o ne or two thin (similar to 2 nm) layers of GaP between the GaInP and G aAs layers. A so-called ''deep emission'' band at 1.46 eV is observed in all our samples. However, at high excitation power, an emission abo ve the band gap of GaAs (previously identified as quantum well emissio n) emerges only in structures where GaP layers are inserted on both si des in between the GaAs well and its GaInP barriers. From the pressure dependence we have identified the deep emission peak as due to donor- acceptor pair transitions at the GaAs/GaInP interface. The insertion o f GaP layers between the GaInP (ordered) and GaAs layers helps to supp ress the defects which contribute to this deep emission. By applying p ressure to the sample which exhibits quantum well emission we have det ermined its band alignments. We show that the GaP layers form two effe ctive barriers for confining electrons within the GaAs well. However, the magnetic field dependence of the quantum well emission reveals tha t the electrons form only a quasi-two-dimensional gas inside the GaAs well. (C) 1998 American Institute of Physics. [S0021-8979(98)05117-2].