Study of Amorphous Gallium Arsenide Films Using a Novel Evaporator with Nondestructive Pickup Image and Electron Diffraction Pattern Investigations

In order to investigate the structure of amorphous gallium arsenide (a-GaAs) targets we developed a novel evaporator attached to an inspection chamber wherein an electron beam serves as both a television (TV) scanning beam and an electron diffraction beam. GaAs targets fabricated by a flash evaporation method at a substrate temperature of above 220°C consist of polycrystalline GaAs (poly-GaAs), the grain size of which is 75Å, and have an electron mobility of 125180 cm2/ Vs. GaAs targets fabricated at a substrate temperature below 200°C are amorphous. We identified two bond lengths, 2.48 Å and 4.00 Å, in radial distribution function (RDF) analyses. These values indicate the interatomic bond lengths of Ga-As and Ga-Ga or As-As, respectively. The including angle of an isosceles triangular molecule of As-Ga-As or Ga-As-Ga is 107.5°. The standard deviations of the bond lengths are 0.145 Å for the 2.48 Å peak and 0.348 Å for the 4.00 Å peak. The electron mobility of a-GaAs is 0.170.45 cm2/ Vs. The resistivities of poly-GaAs and a-GaAs targets are 102Ωcm and 107 Ωcm, respectively. Moreover, we achieved a high resolution of pick-up images on an a-Se/ a-GaAs target.