  A critical requirement for high gain and low noise avalanche photodiodes is
the single-carrier avalanche multiplication. We propose that the single-carrier
avalanche multiplication can be achieved in materials with a limited width of
the conduction or valence band resulting in a restriction of kinetic energy for
one of the charge carriers. This feature is not common to the majority of
technologically relevant semiconductors, but it is observed in chalcogenides,
such as Selenium and compound I2-II-IV-VI4 alloys.
