Growth of GaInP layers on Ge vicinal substrates for multi-junction solar cells

In this research, we studied the growth of GaInP layers on Ge substrates for applications to multijunction solar cells. GaInP layers were grown on p-Ge(100) substrates with 6 .deg. off toward <111> by using low pressure metal-organic chemical vapor deposition (MOCVD). The growth temperature, mass flow ratio of group III materials and V/III ratio were varied in order to grow high-quality GaInP epitaxial layers. A GaInP layer with a 1.6-nm root-mean-square roughness was obtained at a 55% In content. The doping profile in the GaInP and the Ge was characterized by using electrochemical capacitance voltage (ECV) measurements. The junction depth in the Ge substrate due to the diffusion of group V atoms from the GaInP layer was observed to be about 170 nm and did not increase significantly during the subsequent 1000-sec annealing.