Method for testing a wafer and wafer

A method for performing a functional test on a wafer, the method comprising:

• providing the wafer with a semiconductor layer sequence arranged on a substrate;
• attaching at least one first contact element to a main surface of the semiconductor layer sequence facing away from the substrate;
• attaching at least one second contact element to the main surface of the semiconductor layer sequence at a distance to the first contact element;
• and
• applying a first electrical potential to the first contact element and a second electrical potential to a second contact element, wherein the first electrical potential and the second electrical potential are different from each other,
• wherein, by locally annealing the semiconductor layer sequence, a first contact region is formed in a region of the first contact element and a second contact region, which is spaced apart from the first contact region, is formed in a region of the second contact element.

A wafer comprising:

• a substrate and a semiconductor layer sequence arranged on the substrate and having a main surface facing away from the substrate,
• wherein at least one first electrical contact element and at least one second electrical contact element apart from the first electrical contact element are arranged at the main surface,
• wherein the semiconductor layer sequence has a locally elevated temperature in a region of the first contact element and the second contact element,
• wherein the first contact element is configured to receive a first electrical potential,
• wherein the second contact element is configured to receive a second electrical potential, and
• wherein the first and second electrical potential are different from each other.