Method for preparing a germanium substrate and germanium substrate structure for epitaxial growth of a germanium layer

A method for preparing a germanium substrate (1) for epitaxial growth of a germanium layer (7), comprising the following method steps:

• A. providing a germanium substrate (1) having a processing side and a rear side opposite the processing side, and electrochemical processing at least of the processing side of the germanium substrate (1) with at least the following processing steps:
• A.0 passivating the processing side, the processing side being polarized as a cathode,
• A.1 etching of the processing side, the processing side being alternately polarized in an anode pulse as an anode and in a cathode pulse as a cathode,
• A.2 electrochemical passivation of the processing side of the germanium substrate (1), the processing side being polarized as a cathode,
• A.3 etching of the processing side, the processing side being alternately polarized in an anode pulse as an anode and in a cathode pulse as a cathode;
• B. reorganization of the processing side, the germanium substrate (1) being heated to a temperature of greater than 500° C.;
• wherein in method step A.2 a current density is in a range from 0.5 mA/cm2 to 2 mA/cm2.

A method for preparing a germanium substrate (1) for epitaxial growth of a germanium layer (7), comprising the following method steps:

• A. providing a germanium substrate (1) having a processing side and a rear side opposite the processing side, and electrochemical processing at least of the processing side of the germanium substrate (1) with at least the following processing steps:
• A.0 passivating the processing side, the processing side being polarized as a cathode,
• A.1 etching of the processing side, the processing side being alternately polarized in an anode pulse as an anode and in a cathode pulse as a cathode,
• A.2 electrochemical passivation of the processing side of the germanium substrate (1), the processing side being polarized as a cathode,
• A.3 etching of the processing side, the processing side being alternately polarized in an anode pulse as an anode and in a cathode pulse as a cathode;
• B. reorganization of the processing side, the germanium substrate (1) being heated to a temperature of greater than 500° C. U;
• wherein in method step A.3 an etching current density is in a range from 2 mA/cm2 to 15 mA/cm2, and a duration of the anode pulse is in a range from 0.5 s to 2.5 s.

A method for preparing a germanium substrate (1) for epitaxial growth of a germanium layer (7), comprising the following method steps:

• A. providing a germanium substrate (1) having a processing side and a rear side opposite the processing side, and electrochemical processing at least of the processing side of the germanium substrate (1) with at least the following processing steps:
• A.0 passivating the processing side, the processing side being polarized as a cathode,
• A.1 etching of the processing side, the processing side being alternately polarized in an anode pulse as an anode and in a cathode pulse as a cathode,
• A.2 electrochemical passivation of the processing side of the germanium substrate (1), the processing side being polarized as a cathode,
• A.3 etching of the processing side, the processing side being alternately polarized in an anode pulse as an anode and in a cathode pulse as a cathode;
• B. reorganization of the processing side, the germanium substrate (1) being heated to a temperature of greater than 500° C.;
• wherein in method step A.3 a duration of the anode pulse is shorter than a duration of the cathode pulse.

A method for preparing a germanium substrate (1) for epitaxial growth of a germanium layer (7), comprising the following method steps:

• A. providing a germanium substrate (1) having a processing side and a rear side opposite the processing side, and electrochemical processing at least of the processing side of the germanium substrate (1) with at least the following processing steps:
• A.0 passivating the processing side, the processing side being polarized as a cathode,
• A.1 etching of the processing side, the processing side being alternately polarized in an anode pulse as an anode and in a cathode pulse as a cathode,
• A.2 electrochemical passivation of the processing side of the germanium substrate (1), the processing side being polarized as a cathode,
• A.3 etching of the processing side, the processing side being alternately polarized in an anode pulse as an anode and in a cathode pulse as a cathode;
• B. reorganization of the processing side, the germanium substrate (1) being heated to a temperature of greater than 500° C.;
• and
• in a method step A.1A, between method step A.1 and A.2, etching the processing side with an etching current density that is higher than method step A.1, the processing side being alternately polarized in an anode pulse as an anode and in a cathode pulse as a cathode,
• and an anode pulse duration is shorter than a cathode pulse duration.

A method for preparing a germanium substrate (1) for epitaxial growth of a germanium layer (7), comprising the following method steps:

• A. providing a germanium substrate (1) having a processing side and a rear side opposite the processing side, and electrochemical processing at least of the processing side of the germanium substrate (1) with at least the following processing steps:
• A.0 passivating the processing side, the processing side being polarized as a cathode,
• A.1 etching of the processing side, the processing side being alternately polarized in an anode pulse as an anode and in a cathode pulse as a cathode,
• A.2 electrochemical passivation of the processing side of the germanium substrate (1), the processing side being polarized as a cathode,
• A.3 etching of the processing side, the processing side being alternately polarized in an anode pulse as an anode and in a cathode pulse as a cathode;
• B. reorganization of the processing side, the germanium substrate (1) being heated to a temperature of greater than 500° C. U;
• and
• after method step A.3, etching the processing side in a method step A.4, the processing side being alternately polarized in an anode pulse as an anode and in a cathode pulse as a cathode and an anode pulse duration is longer than a cathode pulse duration.

A germanium substrate structure having a germanium substrate (1) produced by a method comprising the following method steps:

• A. providing a germanium substrate (1) having a processing side and a rear side opposite the processing side, and electrochemical processing at least of the processing side of the germanium substrate (1) with at least the following processing steps:
• A.0 passivating the processing side, the processing side being polarized as a cathode,
• A.1 etching of the processing side, the processing side being alternately polarized in an anode pulse as an anode and in a cathode pulse as a cathode,
• A.2 electrochemical passivation of the processing side of the germanium substrate (1), the processing side being polarized as a cathode,
• A.3 etching of the processing side, the processing side being alternately polarized in an anode pulse as an anode and in a cathode pulse as a cathode;
• B. reorganization of the processing side, the germanium substrate (1) being heated to a temperature of greater than 500° C.;
• and a germanium layer (7) epitaxially applied to the germanium substrate (1),
• the germanium layer (7) has p-type or n-type doping with a doping concentration of greater than 1015 cm−3,
• the germanium substrate (1) has at least one porous layer having a thickness in a range from 0.1 to 1.5 μm and a porosity of greater than 40% which is arranged on a processing side of the germanium substrate and has a growth layer terminating the germanium substrate (1) at the processing side and having a thickness in a range from 1 μm to 2 μm and a porosity of less than 5%, and
• the germanium layer (7) has an irregular, pyramid-shaped structure on a surface facing the porous layer.