Growth of Al _0.3 Ga _0.7 As by molecular beam epitaxy in the forbidden temperature range using As ₂

Abstract

Using a thermal cracker and polycrystalline arsenic source material, dimeric arsenic was obtained and utilised to grow Al0.3Ga0.7As layers in the temperature range of 600–700°C with excellent surface morphologies. It has been previously found that, with tetrameric arsenic, excellent surface morphologies were possible only below 630°C and above 690°. Based on these observations, it is postulated that above 630°C tetrameric arsenic has a surface lifetime that is too short to provide enough coverage even when the beam flux is increased dramatically. At and above 700°C, tetrameric arsenic is cracked more effectively by the surface energy gained from the substrate leading to a good surface coverage and to good surface morphologies.