You can find this in the Doctrine documentation:
Doctrine2 : one-to-one unidirectional mapping
I assume in ZF2/Doctrine2 you will have to put "ORM\" before the Doctrine annotations:
/**
* @ORM\OneToOne(targetEntity="Shipping")
* @ORM\JoinColumn(name="shipping_id", referencedColumnName="id")
*/
(edit: added zf2 variant of annotation)