This letter reports on room-temperature electrical measurements of a Au/Ti- HfO2-InP/InGaAs diode fabricated by atomic layer deposition and electron beam lithography. At forward bias voltages, the diode shows memristor characteristics, whereas at reverse bias voltages, the diode can be characterized as a memcapacitor. A parasitic accumulation layer of charges formed at the high- κ oxide/InP interface is shown to be the cause for the phenomena. The operation of the diode as a rewritable memory cell is also demonstrated. The results highlight novel memristive and memcapacitive properties of high-κ dielectrics on III-V semiconductors and their potential applications in nanoelectronics.