Doping is a process in which impurities are intentionally added to a semiconductor to alter its electrical properties. In the case of germanium metal, doping it with a small amount of indium can result in the formation of a p-type semiconductor.

Understanding Doping and Semiconductors:
Semiconductors are materials that have an electrical conductivity between that of conductors and insulators. They have a band gap, which is the energy difference between the valence band (comprised of electrons) and the conduction band (comprised of holes). The band gap determines the electrical behavior of the material.

Doping involves introducing impurities into the crystal lattice of a semiconductor material. These impurities can be classified as donors or acceptors, depending on whether they introduce extra electrons or holes in the material.

Types of Semiconductors:
There are two types of semiconductors based on the type of impurity added during doping:

1. N-type Semiconductor: In an n-type semiconductor, donor impurities are added, which provide extra electrons to the crystal lattice. These donor impurities have more valence electrons than the atoms they replace. As a result, the extra electrons become the majority charge carriers, and the material exhibits negative conductivity.

2. P-type Semiconductor: In a p-type semiconductor, acceptor impurities are added, which create holes in the crystal lattice. These acceptor impurities have fewer valence electrons than the atoms they replace. The holes created can accept electrons from neighboring atoms, making them the majority charge carriers. The material exhibits positive conductivity.

Doping Germanium with Indium:
In the given scenario, germanium metal is doped with a small amount of indium. Indium is an acceptor impurity in germanium and has one less valence electron than germanium. When indium atoms replace germanium atoms in the crystal lattice, they create holes in the structure.

Result:
As a result of the doping process, germanium becomes a p-type semiconductor. The indium impurities create holes in the crystal lattice, and these holes become the majority charge carriers. The presence of the holes allows for the conduction of positive charges, resulting in positive conductivity.

Therefore, the correct answer is option 'D' - p-type semiconductor.