In a study aimed at developing methods for the control of nucleation and growth mode of a III-V semiconductor on large-area glassy substrates by metalorganic chemical vapour deposition (MOCVD), we have utilised the technique of surface photoabsorption (SPA). Although SPA at the appropriate photon energy and angle of incidence is known to be sensitive to the chemical and electronic structure of the surface layers the only features we observe in the transient SPA responses from a variety of glassy substrates are those, which may be attributed to (a) periods where the optical response is constant under conditions where the growth precursors are known to be interacting with the surface, which we attribute to nucleation delays of varying length and (b) interference and roughness effects arising from the deposition of relatively thick layers. From interference oscillations recorded at a wavelength of 633 nm we calculate the growth rate of InP and GaP on a variety of substrates. It is found under the conditions employed that the growth of InP generally occurs more readily than the growth of GaP and also that tin oxide coated glass is the most reactive substrate, exhibiting no nucleation delay. We tentatively attribute the enhanced reactivity of this substrate to the presence of metallic tin, formed via reduction of the tin oxide under hydrogen during substrate preparation. This proposal is supported by X-ray diffraction data. These observations are discussed in terms of the likely nucleation and growth behaviour of the InP and GaP deposits in relation to the growth conditions and the nature of the substrate surface. (C) 1998 Elsevier Science B.V. All rights reserved.In a study aimed at developing methods for the control of nucleation and growth mode of a III-V semiconductor on large-area glassy substrates by metalorganic chemical vapour deposition (MOCVD), we have utilised the technique of surface photoabsorption (SPA). Although SPA at the appropriate photon energy and angle of incidence is known to be sensitive to the chemical and electronic structure of the surface layers the only features we observe in the transient SPA responses from a variety of glassy substrates are those, which may be attributed to (a) periods where the optical response is constant under conditions where the growth precursors are known to be interacting with the surface, which we attribute to nucleation delays of varying length and (b) interference and roughness effects arising from the deposition of relatively thick layers. From interference oscillations recorded at a wavelength of 633 nm we calculate the growth rate of InP and GaP on a variety of substrates. It is found under the conditions employed that the growth of InP generally occurs more readily than the growth of GaP and also that tin oxide coated glass is the most reactive substrate, exhibiting no nucleation delay. We tentatively attribute the enhanced reactivity of this substrate to the presence of metallic tin, formed via reduction of the tin oxide under hydrogen during substrate preparation. This proposal is supported by X-ray diffraction data. These observations are discussed in terms of the likely nucleation and growth behaviour of the InP and GaP deposits in relation to the growth conditions and the nature of the substrate surface. (C) 1998 Elsevier Science B.V. All rights reserved.