Polar Resistors Asymmetric Semiconductor Structures as Linear Resistors with Different Resistances for Opposite Polarities

Abstract

Passive, two-terminal resistors, with linear current voltage relationships, but exhibiting different resistances for opposite polarities are introduced in this paper. Such resistors change their resistance when current direction through them changes. These are named polar resistors. Such polar resistance is observed in asymmetric semiconductor INI structures, where I is an abbreviation for intrinsic, and N is for n-type doped. Polar resistance is not material specific. Both Silicon and Gallium Arsenide polar resistors were simulated in this work. In a three-layered INI structure, for certain thicknesses of the intrinsic layers, it is observed that for positive voltage, voltage drops significantly across one intrinsic layer, and for negative voltage, voltage drops significantly across the other intrinsic layer. With different I-layer thicknesses polar resistance is achieved.  A background mobile electronic concentration of 10¹¹/cc and 10¹²/cc are assumed for Si, due to background doping, and 10⁷/cc and 10⁸/cc are assumed for GaAs.  Metallic ohmic contacts to semiconductor intrinsic layers are difficult to fabricate. So doped n-type CdS and SnO2 were used as contact enabling layers to Si and GaAs respectively. This implies the structure is NININ; i.e. N-CdS/I-Si/N-Si/I-Si/N-CdS and N-SnO₂/I-GaAs/N-GaAs/I-GaAs/N-SnO₂.  In such devices, between -1V and +1V, polar resistance is observed and a rectification ratio up to 10 are demonstrated. The roles of the 
middle N layer and the n-type contact enabling layers are also discussed.