ZINC ION-IMPLANTATION AS A PREDEPOSITION PROCESS IN GALLIUM-ARSENIDE

Ion implantation of zinc into n-type GaAs substrates at room temperature is used as a process of predepositing a solid source from which impurities may be thermally diffused during a postannealing treatment at high temperature (830° or 900°C). The implantation is performed through a Si3N4 layer (about 700Å thick) deposited on the crystal surface, in order to prevent the dissociation of the lattice and the out-diffusion of doping atoms. Due to this fact, the total implanted dose is shared between the superficial nitride layer and the semiconductor. High doses are used around 1015-5 × 1015 ions implanted in the substrate per square centimeter to give rise to a deep junction depth (~10 μm) required for electroluminescence. Such a deep junction is easily obtained by using a high total dose (1016 cm-2) and a high dose inside the GaAs substrate (5 × 1015 cm-2). This paper intends to point out that a high junction depth may also be performed with a high total dose (1016 cm-2) and a weak amount of ions implanted in the semiconductor (1015 cm-2) which comes from the use of a weak implantation energy. This very case is found favorable to good quality doped material. Diodes obtained by this process exhibit good electrical characteristics; evidence of the quality of the resulting p-n junction. Finally, this method leads to light emission efficiency about 1.5 times greater than the standard vapor-phase diffusion, which. proves both the efficient injection of minority carriers and the good quality of the implanted and annealed material. © 1978, The Electrochemical Society, Inc. All rights reserved.