We have designed and fabricated high speed double heterostructure step recovery diodes based on heterojunctions and graded AlxGa1~xAs/GaAs(x \ 0È0.15) intrinsic layers. The IIIÈV compound semiconductor layers were grown by using MOVPE (Metal Organic Vapor Phase Epitaxy) technique, whereafter the diode structure was mesa etched. The ohmic contacts were made by using Ti/Au layers on the front contact and Ni/AuGe/Ni/Au layers on the backside. The measured ideality factor of the diode was 1.95, and the capacitance under forward bias was 108 pF, and 0.9 pF under reverse bias. The measured transition time was 50 ps.