The Mystery of the Mass of a Vacancy

[tina_singh]

a hole is the absence of electron..so basically its just a vacancy..
so why does it have a mass??..how can a vacancy have a mass and dat too greater than electron itself??..can any1 pleasez help..

 

[Cthugha]

Two comments: First, in semiconductor physics the electron and hole masses given are effective masses which means that the effect of having a lattice and interactions is incorporated into the mass, thus making it an effective mass which is very different from the bare electron mass. Second, for a hole to move around, electrons need to move around, too. They have to rearrange such that the vacancy (the hole) moves around. Depending on the material you examine, the motion of a single electron and the collective motion of many electrons which constitutes hole motion may be influenced differently by the presence of the periodic lattice. Therefore the masses may differ.

 

[technician]

When an electron is released from a bond it becomes 'free' and can move under the influence of electric (and magnetic) fields. This causes electrical conduction and it is logical to refer to the mass of an electron.
A hole is the vacancy left by the electron and behaves as a + charge. Electrons can move into the hole and therefore the hole can be considered to move. Even though movement of the hole is just another version of moving electrons it is convenient to consider the holes as + charged particles. They will move under the influence of electric (and magnetic) fields and to describe their motion they can be assigned a mass.