Crystal growth of compound semiconductor mixed crystals under controlled vapor pressure

A solution growth method for producing a compound semiconductor mixed crystal of the formula:

• GaAs.sub.1-x P.sub.x
• where 0<.times.>1,
• said method comprising the steps of:
• (1) providing a first crucible and a second crucible for double epitaxial growth,
• (2) introducing into each of the crucibles a solution of source material and solid source material containing a volatile element therein in contact with said solution and supplying said crucibles from the same pressure source with said volatile element at a pressure for conducting successive epitaxial growth under a controlled vapor pressure condition;
• (3) controlling the temperature of said first crucible independently of the temperature of said second crucible to establish in each of said crucibles a temperature difference between a top portion and a bottom portion of said solutions and adjusting the temperature of each of said crucibles at respective constant values;
• (4) applying to each of said solutions a controlled vapor pressure of each of the volatile elements contained in said source material through a thin tube from a pressure source separate from the crucible, said volatile elements having a relatively higher vapor pressure;
• (5) positioning a substrate for epitaxial growth on a slider adapted to be contacted with the low temperature portion of said solution;
• and
• (6) successively growing epitaxial layers of said compound semiconductor mixed crystal on said substrate positioned at the bottom portions of said first and second crucibles while said source material remains at the top portion of each of said crucibles or said solution;
• wherein said source material and said vapor pressure are selected to provide a substantial coincidence of the composition of said epitaxial layer with said source material and the epitaxial layers of said compound semiconductor mixed crystal, said crystal exhibiting optimum performance of a predetermined physical property.

A solution growth method for producing III-V mixed crystals from a solution, comprising the steps of:

• (1) introducing into a crucible a solution of source material and thereon a solid source material containing volatile elements therein, said crucible having a source-feeding portion and a crystal growing portion;
• (2) providing a substrate on a slider adapted to contact the crucible at the crucible growing portion thereof;
• (3) controlling the temperature in the crucible to establish a temperature difference between the source-feeding portion and the crystal-growing portion and to maintain the temperature of the respective portions at respective constant predetermined values;
• (4) applying, during epitaxial growth, a vapor pressure of each of the Group V elements of the constituents of said mixed crystal, the vapor pressure being in the range between 1.93.times.10.sup.6 exp (-1.01/KT.sub.g) and 4.61.times.10.sup.6 exp (-1.01/KT.sub.g),
• wherein K represents the Boltzmann constant, Tg represents the growth temperature in degrees Kelvin, and KT.sub.g is expressed in electron volt units;
• and
• (5) growing an epitaxial layer of said III-V mixed crystal on a substrate disposed at said crystal-growing portion while said vapor pressure is applied and said source material remains at said source-feeding portion;
• wherein the vapor pressures are selected at such values that the epitaxial layer of the III-V mixed crystal has substantially the same composition as that of said source material for establishing a steady state during crystal growth.

An apparatus for producing compound semiconductor mixed crystals, comprising:

• at least two substantially closed crucibles each adapted to contain a solution of source material and solid source material therein, including a top and a bottom portion, the bottom of each such crucible having means for growing the mixed crystal contained therein successively and epitaxially on a substrate mounted on a carrier means disposed at the bottom of each of the crucibles;
• a heating means for establishing a temperature difference between a top portion and a bottom portion of each said solution such that the temperature of said top portion is higher than the temperature of said bottom portion, the temperature difference between the two portions being held at substantially constant values;
• at least two thin tubes each communicating with each of said crucibles at one end with the inside of a space located above said top portion in each said crucible and having a lower temperature feeding section located at the opposite end to contain therein one of at least two volatile elements of said mixed crystal;
• and
• at least two heating means for controlling temperatures of said lower temperature feeding sections independently of one another and thereby providing controlled vapor pressures;
• said heating means adapted to provide optimum vapor pressures of said volatile elements for conducting successive epitaxial growth under a controlled vapor pressure required for growing epitaxial layer having substantially the same composition as that of said source material.