Method for growing a single crystal of compound semiconductor

Claim 1

A method for growing a single crystal of compound semiconductor comprising the steps of: melting a liquid encapsulant material and compound semiconductor material doped with one or more than one impurities which have a distribution coefficient less than 1 and are selected from In, B, Sb, Si, Ga, As or P; dipping a seed crystal into the material melt covered with the liquid encapsulant; and growing a single crystal from the melt by pulling up and rotating the seed crystal; characterized in that the pulling speed R is lowered from an initial pulling speed so as not to exceed a critical pulling speed R* during the period of substantial crystal growth, where R* is given by R*=(QG.sub.l /w.sub.o)(1-g).sup.1-k where w o is an initial gram equivalence of impurity, G l is the temperature gradient in the material melt, g is the fraction solidified to the initial material melt, k is the distribution coefficient of impurity, and Q is a constant value defined by Q=D/227(1-k) where D is the diffusion constant of the impurity in melt, and k is the equilibrium distribution coefficient of the impurity.

Claim 2

A method for growing a single crystal of compound semiconductor comprising the steps of: melting a liquid encapsulant material and compound semiconductor material doped with one or more than one impurities which have a distribution coefficient less than 1 and are selected from In, B, Sb, Si, Ga, As or P; dipping a seed crystal into the material melt covered with the liquid encapsulant; and growing a single crystal from the melt by pulling up and rotating the seed crystal; characterized in that the pulling speed R is lowered from an initial pulling speed so as not to exceed a critical pulling speed R* during the period of substantial crystal growth, where R* is given by R*=(QG.sub.l /w.sub.o)(1-g).sup.1-k where w o is an initial gram equivalence of impurity, G l is the temperature gradient in the material melt, g is the fraction solidified to the initial material melt, k is the distribution coefficient of impurity, and Q is a constant value defined by Q=D/227(1-k) where D is the diffusion constant of the impurity in melt, and k is the equilibrium distribution coefficient of the impurity.

Claim 3

A method for growing a single crystal as claimed in claim (1), wherein the melt is a GaAs melt, the doped impurity is In or B and the impurity concentration at the top porton of a pulled crystal is 5×10 18 cm -3 to 8×10 19 cm -3 .

Claim 5

A method for growing a single crystal as claimed in claim (1), wherein as a function of fraction solidified g, the pulling speed R is given by R=R.sub.0 (1-g).sup.1-h where R 0 is an initial pulling speed, h is a positive constant less than 1 and g is a fraction solidified which is a quotient of the weight of the solidified part divided by the initial weight of melt.

Claim 6

A method for growing a single crystal as claimed in claim (1), wherein a magnetic field is applied to the melt during the growth.