EFFECTS OF THE In AND N DISTRIBUTION ON NANO-SCALE STRUCTURES IN NEARLY LATTICE-MATCHED InGaPN ON GaAs (001) GROWN BY MOVPE

Abstract

Abstract In the dissertation, an effect on N incorporation on alloy fluctuation, structural ordering and non-radiative recombination in the InGaPN films on GaAs (001) substrates are systematically investigated. All the InGaPN films were grown by metalorganic vapor phase epitaxy (MOVPE) with different DMHy flow rates of 0, 300, 700 and 1,100 mmol/min. To improve crystal quality, the InGaPN films were thermally annealed using rapid thermal annealing (RTA) process, which was performed at 650 OC for 30, 60, 120 and 180 seconds under N2 ambient. To examine the In and N contents, a combination of HRXRD and Raman spectroscopy measurements has been applied for the nearly lattice-matched InGaPN films grown on GaAs (001) substrates. The structural ordering was measured by the Raman spectroscopy and the non-radiative recombination center are studied by room temperature photoluminescence (PL) spectroscopy. According to Raman scattering results, the In content, which is slightly effected by an introduction DMHy during the growth, was determined to be 56.4±0.8 at%, 55.8±0.8 at%, 55.9±0.9 at% and 55.7±1.1 at% with increasing DHMy flow rates from 0 to 1,100 µmol/min. Consequently, the N content was determined to be 0, 0.9±0.4 at%,1.4±0.4 at% and 2.1±0.5% with increasing DHMy flow rates. Raman spectroscopy results show a weak structural ordering to be the level that no effect on an optical bandgap. Decreasing of an integrate intensity of PL spectra with increasing of the N content indicates an increase of the non-radiative recombination centers. After RTA process, PL spectra exhibited higher intensity. This indicates a reduction of the non-radiative recombination centers. The InGaPN samples were annealed at 650 OC at 30, 60, 120 and 180 seconds. Further, HRXRD results show a reduction of alloy fluctuation due to crystal reorganization mechanism. The increasing of N content, which results in an increase of structural ordering, was observed after RTA. The best film quality with lowest misfit strain of 0.12% was obtained for the InGaPN film grown with DMHy flow rate of 1,100 µmol/min and annealing time of 120 s.