Growth and photoluminescence investigations of phosphorus- and iodine-doped MOVPE ZnTe layers

Abstract

ZnTe layers doped with phosphorus and iodine were grown on (001)-GaAs substrates by atmospheric-pressure metalorganic vapour phase epitaxy (MOVPE). Temperature-dependent near-band-gap photoluminescence allowed the ground state of phosphorus acceptors ( E 1 S 3 2 P = 62 meV ) to be determined. Resonant excitation methods as selective-pair luminescence (SPL) and two-hole transitions (THTs) enabled the investigation of excited acceptor states in epitactically grown ZnTe layers. The energy levels of these excited states of phosphorus acceptors investigated in free-standing layers have led to the Luttinger parameters γ 1=0.72 and γ 3=1.3. Iodine-doped ZnTe layers showed strong emission bands at 2.24 and 2.22 eV. Their intensities were found to be dependent on the partial pressure ratios of the iodine organyl to the tellurium bands during growth. The first emission band is due ro the incorporation of impurity atoms with a binding energy of about 145 meV, which is in a good agreement with the binding energy of copper in ZnTe. The emission band at 2.22 eV is assigned to zinc-vacancy-iodine complexes (V Zn-I). A binding energy of 170 meV of these luminescence centres was derived from temperature-dependent measurements.