Reduction of nonradiative recombination center for ZnO films grown under Zn-rich conditions by metal organic chemical vapor deposition

Abstract

ZnO films were grown by metalorganic chemical vapor deposition using the repeated temperature modulation in an H2 ambient. The crystalline quality, as defined by the full-width at half-maximum of the ω (101¯1) reflection, was found to be correlated with the photoluminescence (PL) lifetime at 300 K. The fine structure of the PL spectra for the samples grown under Zn-rich condition at 8 K indicated the higher order (n=2) structure of free exciton A, two electron satellites and phonon-replicas. The internal quantum efficiency and the PL lifetime at 300 K were 5.5% and 2.6 ns, respectively, indicating a reduction in Zn vacancies in the ZnO films.

High reactivity of H 2 O vapor on GaN surfaces

“…The amount and rate of oxygen adsorbed on the surfaces were larger and higher than in the case of O 2 gas. The dependence of oxygen adsorption on GaN surfaces was opposite to the oxidation power for bulk metals (H 2 O ≪ O 2 < NO, N 2 O) under equilibrium condition [ 14 , 15 ]. The DF-MD calculation was carried out in order to understand the larger oxygen adsorption on GaN surfaces caused by H 2 O vapor in spite of its lower oxidation power.…”

Controlling the carrier lifetime of nearly threading-dislocation-free ZnO homoepitaxial films by 3d transition-metal doping

“…15 For comparison, R q À s PL relationships reported for UID-ZnO epilayers grown by laser-assisted molecular-beam epitaxy (L-MBE), 15 plasma-assisted molecular-beam epitaxy (PA-MBE), 21 and metalorganic chemical vapor deposition (MOCVD) 22,23 are plotted. In these epilayers, 15,[21][22][23] major NRCs are the "native" one, V Zn X. 14,15 It is obvious that the plots of TM-doped and UID ZnO lie on the same line.…”

“…15 For comparison, R q À s PL relations reported for UID ZnO epilayers 15,[21][22][23] are plotted (square, circles, and triangles). The major NRCs in those samples 15,[21][22][23] are "the native" one, V Zn X. 14,15 MOCVD are lower than 1 Â 10 16 cm À3 .…”

“…The exciton capture-cross-section (r ex ) is estimated to be 2.4 Â 10 À15 cm 2 . From the linear dependence of R q on s PL found universally in the epilayers containing native-NRCs 15,[21][22][23] and TMs, the concentrations of native-NRCs ([V Zn X]) in unintentionally doped (UID) ZnO in literatures [2][3][4]14,15,[21][22][23] are estimated to be "lower than" 10 16 -10 17 cm À3 .…”

Cathodoluminescence study of optical properties along the growth direction of ZnO films on GaN substrate

“…1 Introduction ZnO is an important semiconductor for the UV emitting devices due to the wide direct bandgap and high exciton binding energy [1][2][3]. Substrates such as GaN or sapphire are used for the epitaxial growth of ZnO films [4,5]. Compared to the sapphire substrates, the lattice mismatch between GaN and ZnO is as small as 2%, which promises the growth of high quality ZnO films on GaN substrates [6].…”