Resistance and 1/f noise of Au, Al, and Ge contacts to (Hg,Cd)Te

The resistance and 1/f noise of Au and Al contacts to ion-sputtered p-type Hg0.79Cd0.21Te and of Ge contacts to Hg0.7Cd0.3Te have been measured at temperatures of 12, 40, 77, and 295 K. The Au and Al contacts were ohmic at all temperatures whereas the Ge contacts were partially rectifying. The specific contact resistance for Au and Al varied by about a factor of 10 up to 9×10−4 Ω cm2 and 3×10−3 Ω cm2, respectively, at 295 K, and there was little variation in resistance down to 12 K. The 1/f noise of the Au and Al contacts could be described as a power spectral density of resistance fluctuations SR which varied with the contact diameter d as SR∝d−m, where 5≤m≤6 for Au and 2≤m≤3 for Al. The values of m suggest that whereas the 1/f noise of the Au contacts originated at the Au/(Hg,Cd)Te interface or in the underlying (Hg,Cd)Te, the 1/f noise of the Al contacts originated in a surface conduction layer next to the contact. The magnitude of the 1/f noise was significantly larger than expected for any fundamental 1/f noise source.