Nondestructive assessment of In-0.48(Ga1-xAlx)(0.52)P films grown on GaAs (001) by low pressure metalorganic chemical vapor deposition

The quaternary alloy In 0.48 (Ga1-xAlx)(0.52)P, lattice-matched to GaAs, ha s a direct band gap transition in the wavelength range of green-red light a nd is useful in optoelectronic applications such as visible light emitting diodes and laser diodes. We have investigated a set of six nominal In-0.48( Ga1-xAlx)(0.52)P layers that were grown on GaAs (001) by low pressure metal organic chemical vapor deposition (MOCVD) turbo disk technology. In order t o control and optimize the growth conditions to produce high quality InGaAl P epilayers, a variety of nondestructive techniques, including photolumines cence (PL), Raman scattering, photoreflectance (PR), reflectance anisotropy (RA) spectroscopy, atomic force microscopy (AFM), and high resolution x-ra y diffraction (HRXRD) have been applied to evaluate the epitaxial films and growth processes. HRXRD confirmed a good lattice match between the epilaye rs and the substrate material. The PL and PR spectra showed the variations of the InGaAlP PL peak and the energy band with growth pressure and other p arameters. Raman spectral line shape analysis leads to information about th e sample crystalline quality. Polarization dependent PR and RA spectroscopy were used to detect the in-plane anisotropy of epitaxial materials. AFM wa s used to study the surface morphology of these quaternary compounds and to nondestructively detect any possible dislocations in these hetero-epitaxia l materials. The optimized parameters for the growth of high quality InGaAl P films on GaAs were obtained. The combination of these nondestructive tech niques offers a better understanding of MOCVD-grown In-0.48(Ga1-xAlx)(0.52) P/GaAs and a useful way to optimize the growth parameters of high quality q uaternary semiconductor materials. (C) 1999 American Institute of Physics. [S0021-8979(99)04007-4].