How to create a user after ldap authenticaion?
The LDAP module will also allow you to automatically create a user after authentication. 


Once you configure your server, look at the third tab LDAP
authorization Choose edit to configure that server
Under basic, enable and Only apply the following LDAP to drupal role
configuration to users authenticated via LDAP.
You can set the role of the new user by checking  drupal roles are
specified by LDAP attributes under IIB. Also name the field that will
be use to determine role
Configure part III. LDAP to drupal role mapping and filtering For
example, if the title field is Staff you may want to give a staff
role Staff|staff
Part 4    IV.B. When should drupal roles be granted/revoked from
user? Check "When a user logs on"
IV.C. What actions would you like performed when drupal roles are
granted/revoked from user? Check Revoke drupal roles previously
granted by LDAP Authorization but no longer valid.


There are other settings that you can configure but this should get you started.