Epitaxial deposition of GaAs and GaAsP on Ge substrates

Abstract

The successful deposition of GaAsP epitaxial layers on (001) ‐Ge substrates is reported. The Tietjen and Amick vapor‐phase epitaxial technique is applied without modification. Hence the deposition can be transferred to technical production. Autodoping, i.e., the incorporation of Ge atoms in the epitaxial layer, was suppressed by choosing adequate back‐surface passivation layers and by proper control of the epitaxial program steps. Evidence for the suppression of autodoping was given by carrier concentration measurements and by photoluminescence spectroscopy of GaAs layers on Ge substrates. The latter revealed no signs of Ge acceptors in the GaAs epitaxial layers, which means the concentration of Ge must be lower than at least 5×10¹⁴ cm⁻³. Based on this result the deposition of GaAs_1−xP_x on Ge substrates was studied with x?0.38 as an aim. After having attained an acceptable state of progress the layers were tested by zinc diffusion to get p‐n junctions and light‐emitting diodes. Commercial GaAsP samples were simultaneously subjected to the same treatment for control. We finally succeeded in producing diodes emitting red light with a dominant band‐to‐band peak of 15 nm width at room temperature.