Stoichiometric GaAs films have been prepared by RF sputtering over an appreciable range of substrate temperature Ts. The structural and optical properties of these films have been investigated by means of a variety of experimental techniques. Transmission electron microscope (TEM) experiments reveal that for Ts>or= approximately 70 degrees C the structure consists of nanocrystals embedded in an amorphous network. EXAFS, XPS and infrared experiments are consistent with each other, indicating that configurational disorder in the amorphous network of the GaAs films decreases as Ts is raised. Most of the disorder relates to bond-angle disorder; the spread in bond angle around Ga atoms is found to be less than that around As atoms for a given substrate temperature. The changes observed in the fundamental absorption edge with increasing Ts are discussed in relation to various possible defects in amorphous GaAs.

Stoichiometric films of InP have been prepared by rf sputtering over a wide range of substrate temperature Ts. The structural and optical properties of these films have been investigated using several experimental techniques. For Ts ⩽ 100°C TEM reveals that the structure consists of an amorphous network which is shown by EXAFS, optical and XPS data to be largely chemically ordered with few wrong bonds present. For Ts ⩽ 100° C the structure consists of nanocrystals, embedded in an amorphous network, which increase in size with Ts. The decrease in bond angle disorder with increase in Ts has been quantified by both EXAFS and XPS.