Hot carrier injection (HCI) may be used to provide various improvements for one-time programmable (OTP) read-only memory (ROM) or physical unclonable function (PUF) circuits. HCI may be used to write a memory bit (e.g., logical 0 or 1), which may be used in OTP ROM. HCI may be used to provide improved programmable ROM (PROM) memory devices, such as to facilitate programming or to increase sensing window. HCI may also be used to write a memory bit in a PUF circuit. HCI may provide a cross-foundry portable PUF circuit that has an associated adjustable bit error rate (BER), which may be used to secure root key generation, or may be used to provide a unique identification (ID) for fuse replacement.