Carrier freezeout in reverse‐biased Hg0.8Cd0.2Te photodiodes has been investigated to determine the relevant acceptor level. At temperatures between 12 and 21 K hole freezeout in thepregion governs the interband tunneling, which dominates the current across the reverse‐biased photodiode. The acceptor level was found to be ∼4 meV in thep‐type Hg0.8Cd0.2Te substrate withNA−ND∼1016cm −3. In comparison with Hall measurements, this new method avoids the uncertainty due to contact caused by surface inversion onp‐Hg0.8Cd0.2Te. ©1996 American Institute of Physics.