The anneal behavior of Be implantations into undoped InP was studied using a capless, rapid thermal annealing (RTA) process. It is shown that shallow p-type layers in InP can be obtained reproducibly making this process suitable for device fabrication. Maximum hole concentrations and minimum in-diffusion are observed for anneal durations of about 1 minute. Out-diffusion of implanted Be is identified as the main reason for low hole concentrations and can be decreased by co-implanting matrix atoms.