Each semiconductor has different electron affinity and band gap values.

This is the same sign convention as is used for electron affinity.

Likewise electron affinity is a also a positive number.

Li also has the largest electron affinity in this group.

In this case, the atom with the more positive energy value has the higher electron affinity.

As one progresses from left to right across a period, the electron affinity will increase.

In some circumstances, electron affinity may even become negative.

To use electron affinities properly, it is essential to keep track of sign.

This is quite a different matter than electron affinity.

A trend of decreasing electron affinity going down groups would be expected.