CARRIER FREEZEOUT IN N-ON-P HG0.7CD0.3TE PHOTODIODE AND ACCEPTOR LEVEL DETERMINATION

Carrier freezeout has been directly observed in Hg0.7Cd0.3Te photodiod es at temperatures lower than 25 K. The freezeout was seen under the c onditions that interband tunneling dominates the current in the photod iode and that avalanche ionization does not take place. These conditio ns are fulfilled at temperatures lower than 25 K and reverse bias volt ages around 3 V. An acceptor level of about 4 meV was determined for p -type Hg0.7Cd0.3Te with N-A - N-D similar to 10(16) cm(-3) from the te mperature dependence of the photodiode resistance governed by carrier freezeout. The difficulties in observation of carrier freezeout in Hg1 -xCdxTe with a larger composition ratio x or higher doping concentrati on are discussed.