In JPA 2.0+ you can use @JoinColumn as a way to avoid to generate joined table.
Try it.
@OneToMany
@JoinColumn(name="COLUMN_NAME")
UPDATE
The info provided above has been extracted from EJB 3.0 o’reilly book (Look for The @JoinColumn annotation references the CUSTOMER_ID column in the PHONE table). However, plain JPA 1.0 specification does not support this feature. What it says is
Unidirectional one-to-many relationships may be implemented using one-to-many foreign key mappings, however, such support is not required in this release. Applications that want to use a foreign key mapping strategy for one-to-many relationships should make these relationships bidirectional to ensure portability
So in 1.0 it is a vendor-specific implementation (And it makes sense, The author works at JBoss – The red hat divison behind the hibernate)
But it is supported by JPA 2.0 implementation
If the join is for a unidirectional OneToMany mapping using a foreign key mapping strategy, the foreign key is in the table of the target entity.