Dear Marty,
The Church teaches that artificial insemination is wrong even when the donor is alive. God designed conception to take place in the context of the husband and wife consummating the wedding vows that they made at the altar. Procreation is the physical expression of wedding vows. This cannot be duplicated in a Petri dish.
In the case of the donor being deceased, the situation is even a greater evil in that, as you said, the child will be deliberately conceived not having a father in his or her life. How cruel is that?
Fr. Vincent Serpa, O.P.