Siam Physics Congress 2016

8-10 June 2016
Asia/Bangkok timezone

STRUCTURAL, VIBRATIONAL AND OPTICAL PROPERTIES OF THICK GaPN FILMS GROWN ON GaP SUBSTRATE BY MOVPE

Not scheduled
15m
Poster presentation Magnetic and Semiconductor Physics

Description

Structural, vibrational and optical properties of thick GaPN films with the N contents of 0.8, 1.8 and 5.4 at% on GaP (001) substrates have been investigated using high resolution X-rays diffraction technique (HRXRD), Raman spectroscopy and micro-photoluminescence spectroscopy (micro-PL). The GaPN films were grown by metalorganic vapor phase epitaxy (MOVPE) using Tertiarybutylphosphine (TBP) and dimethylhydrazine (DMHy) as Ga, P and N precursors, respectively. The thickness of the films with N contents of 0.8, 1.8 and 5.4 at% was reduced to be 347, 327, 317 nm, respectively. All the films were examined under tensile strain with a partial relaxation. Despite the fact that the GaPN films were incorporated with N as high as 5.4 at%, however, smooth surfaces and fairly flat interfaces are visibly observed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Raman spectra reveal the N-related vibrational modes (N-VMs) in range of 440 – 520 cm$^{-1}$, which is the first observation for the dilute GaPN alloy. The N-VMs intensity exhibits a linear relationship on the N content determined by HRXRD. This confirms that the incorporated N atoms are substituted at the P lattice, resulting in an isolated local vibrational mode and the NN$_i$ pairs related vibrational modes. Room temperature bandgap was obtained by micro-PL is dramatically reduced when the N content is increased. A huge bandgap bowing parameter of the GaPN is calculated to be 10 eV. The relationship between film relaxation and bandgap reduction is carefully concerned.