A new type of green‐light‐emitting negative‐resistance gallium phosphide diode has been produced by diffusing ap‐njunction into a singlen‐type liquid epitaxy growth. This growth includes a narrow high‐resistivity layer introduced by the transient incorporation of deep acceptors. The negative resistance has been shown to be due to optical feedback between the emitting junction and the photosensitive high‐resistivity region. External quantum efficiencies of 0.08% at 565 nm with a current density of 11 A cm−2have been obtained from these devices when used in a true latching mode with a standing bias of 5 V and turn‐on turn‐off pulses of ±4 V.