In Si junction diodes it is possible to achieve a short recombination time together with a large storage time at room temperature by deliberately introducing impurities with asymmetric trapping levels, such as Pt, into the region of the junction. It is shown that this technique can be used in surface‐acoustic‐wave devices to increase the bandwidth by reducing the writing time on a junction memory to 5×10−9sec while the storage time remains above 0.2 sec.