If I saw zera when I woke up, I have to take a shower to be able to pray?
Preferably you should make sure that there is no zera on you before you daven. This is because according to some poskim, zera has a halacha like tzoah. Therefore it should preferably be washed or wiped off before davening. However it is preferable to take a shower. for two reasons. Firstly there is the idea of tevilas Ezra. Ezra instituted that whenever a man has an emission that he should tovel in a mikva before learning torah etc. Although he instituted this idea, nowadays it no longer applies, however it is a pious thing to do. If it is too hard for one to do this, one can pour 9 kavim of water over himself, which can be done by taking a shower. See the following post that talks about this http://dinonline.org/2016/09/18/bath-for-9-kavim/
Secondly ( when applicable) to get rid of it because it is a reminder of a sin, and therefore we would want to get rid of it before davening.
O:CH 76-4, M:B 15, O:CH 68-1, M:B 4.