Study of low temperature growth of III-V alloys for transparent layers
The authors report on the successful growth of wide band gap III-V alloy systems on glass substrates at low growth temperatures that may be suitably exploited for the realization of novel high performance and stable optoelectronic devices. A systematic investigation on the growth of GaAs, GaAlAs(N), and AlAs(N) at low temperatures (< 300 degrees C) on various substrates has been carried out to determine the effects of constituent elements of the alloy and the growth process parameters on the surface morphology and structural and optical properties of the materials. Optimized growth conditions were thus established for the successful growth of GaAlAsN polycrystalline layers with an average transmission of 80% in the visible region, with optical absorption energy >3.0 eV. The surface exhibited meandering cracks, with root mean square roughness of about 1 nm in the smooth areas between the cracks. Peaks observed in the x-ray diffraction and Raman spectra of these layers were relatively sharp in comparison to the other unoptimized quaternary layers, clearly attesting to the better quality of these layers. In addition, these layers exhibit preferential Al-N bond formation as evidenced in the corresponding Raman spectra.