We have fabricatedn‐pjunction photovoltaic detectors in InSb using proton bombardment to create then‐type layer. At 77 °K, diodes which were 20 mils in diameter had zero‐bias resistances of several hundred thousand ohms. The peak detectivity at 4.9 &mgr; of these diodes with a 2&pgr;, 300 °K background was typically greater than 3×1010cm Hz1/2/W with the largest value observed being 1011cm Hz1/2/W. Diode quantum efficiencies near 35% were observed.