INTERFACE-TRAP CONDUCTANCE SPECTROSCOPY OF A NARROW-GAP HG1-XCDXTE (X-APPROXIMATE-TO-0.2) MIS DEVICE

The observation of a pronounced double peak structure in the equivalen t parallel conductance of a metal-insulator-semiconductor (MIS) device prepared on a Bridgman-grown x approximate to 0.2 p-type Hg1-xCdxTe c rystal passivated by an anodic oxide layer is reported, The first peak , placed in the depletion part of the conductance-voltage (G-V) curves , has been attributed to the response of single-level interface traps distributed over the semiconductor gap supposing band-bending fluctuat ions. The second peak, placed at the onset of strong inversion, is due to shunting of the minority carrier flow by the electrons coming from the inverted surface area beyond the gate. An order of magnitude enha ncement of the structure measured on capacitance-voltage (C-V) and G-V curves below T approximate to 10 K has been attributed to hole freeze out, leading to a substantially slower sample response and to an expon ential increase of its series resistance. The tunnelling from acceptor states near the Fermi level to interface traps and/or to light hole s tates in the valence band becomes a competing mechanism to majority ca rrier response in the depletion and accumulation regions in that case.