Method for producing devices comprising high density amorphous silicon or germanium layers by low pressure CVD technique

Abstract

Layers of controllably dopable amorphous silicon and germanium can be produced by means of low pressure chemical vapor deposition, at a reaction temperature between about 450.degree. C. and about 630.degree. C., for Si, and between about 350.degree. C. and about 400.degree. C. for Ge, in an atmosphere comprising a Si-yielding or Ge-yielding precursor such as SiH.sub.4 or GeI.sub.4, at a pressure between about 0.05 Torr and about 0.7 Torr, preferably between about 0.2 and 0.4 Torr. For undoped Si and P-doped Si, the preferred temperature range is from about 550.degree. C. to about 630.degree. C., for B-doped Si, it is from about 480.degree. C. to about 540.degree. C. The material produced has a density in excess of 0.9 of the corresponding crystalline density, and contains less than 1 atomic percent of hydrogen. An advantageous doping method is addition of dopant-forming precursor, e.g., PH.sub.3 or B.sub.2 H.sub.6, to the atmosphere. The material produced can be transformed into high quality crystalline material, and has many device applications in amorphous form, e.g., in solar cells, vidicon tubes, photocopying, and in integrated circuits, either as a conductor or nonconductor. The layers produced show conformal step coverage.

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