Method of growing germanium crystals
In accordance with the present invention, taught is a high purity germanium crystal growth method utilizing a quartz shield inside a steel furnace. The quartz shield is adapted for not only guiding the flow of an inert gas but also preventing the germanium melt from contamination by insulation materials, graphite crucible, induction coil and stainless steel chamber. A load cell provides automatic control of crystal diameter and helps to ensure exhaustion of the germanium melt. The method is both convenient and effective at producing high purity germanium crystals by relatively low skilled operators.
1. A method of growing high purity germanium crystals, comprising the steps of:
(a) isolating a first crucible containing molten germanium inside a melt container comprising a quartz shield having a removable lid;
(b) locating said melt container inside a furnace for controlling the temperature of said germanium;
(c) passing an inert gas through said melt container;
(d) controlling the diameter of a crystal of germanium drawn from said first crucible at a rate controlled by a load scale that monitors the weight of the crystal; and
(f) removing the lid from the quartz shield to permit withdrawl of the germanium crystal from the melt container.
2. The method of claim 1 , wherein said molten germanium has a net carrier concentration between about 10 9 and about 10 10 cm −3 .
3. The method of claim 1 , wherein said quartz shield includes a quartz lid and a quartz tube.
4. The method of claim 3 , further comprising a graphite crucible and wherein the quartz tube is located between the graphite crucible and said first crucible.
5. The method of claim 1 , wherein said inert gas is hydrogen and the flow rate is between about 50 and about 250 L/h.
6. The method of claim 1 , wherein a weigh signal from the load scale is used to modify the temperature of the molten germanium to control the crystal diameter and the exhaustion of all the melt.
7. The method of claim 1 , wherein said crystal of germanium has a dislocation density of between about 10 2 and about 10 4 cm −2 .