Selective doping of conformal GaAs layers grown by hydride vapour phase epitaxy on Si substrates studied by spatially resolved optical techniques

High quality GaAs layers on silicon substrates were grown by conformal growth. In this technique, the GaAs conformal growth is initiated on the sidewalls of GaAs seed stripes (typically 10 μm wide with a pitch of 200 μm) grown conventionally on a Si substrate, and developed inside a cavity formed by the silicon substrate and an overhanging dielectric cap layer. The conformal layers were grown by hydride vapour phase epitaxy (HVPE) and doped with Si or Zn. The properties of these layers were studied by micro-Raman, cathodoluminescence (CL) and micro-photoluminescence (PL). The free carrier concentration was obtained with a micrometric spatial resolution. Both n-type (Si) and p-type (Zn) doping was achieved, showing the feasibility of selective doping and p–n homojunctions.