Formation of p+-p-n junctions in gallium arsenide by a two-step diffusion process

A two‐step, open‐tube diffusion process has been developed to form p +‐p‐n junctions in GaAs. n‐type GaAs substrates were zinc diffused at 550 °C to form a p + layer, capped with thermally deposited silicon nitride, and annealed in an open‐tube furnace. The zinc redistributes during the anneal, forming a p layer adjacent to the p + layer. The peak carrier concentration of the p + and p layers and the depth of the p +‐p and p‐n junctions are controlled by the time and temperature of the anneal. The anneal time was varied from 30 to 180 min and the temperature range was 700–850 °C. Both the p +‐p and p‐n junction depths show a square root dependence on annealing time. Diffusion coefficients and activation energies for the zincdiffusion which occurs during the anneal are determined.