This survey deals with 1/f noise in homogeneous semiconductor samples.
A distinction is made between mobility noise and number noise. It is
shown that there always is mobility noise with an alpha value with a m
agnitude in the order of 10(-4). Damaging the crystal has a strong inf
luence on alpha, alpha may increase by orders of magnitude. Some theor
etical models are briefly discussed; none of them can explain all expe
rimental results. The alpha values of several semiconductors are given
. These values can be used in calculations of 1/f noise in devices.