Non-linear behavior of Al-contacted pure amorphous boron (PureB) devices at low temperatures

Deposition of pure amorphous boron (PureB) layers on n-type Si results in p⁺n-like devices even in cases where B in-diffusion during the deposition is not expected. It is suspected that such behavior is due to the formation of an interfacial hole layer (IHL) between the PureB and Si. To further investigate physical mechanisms governing conduction of holes across the PureB/Si interface and through the IHL, electrical measurements were performed from room temperature down to cryogenic temperatures as low as 100 K. In this paper, current-voltage (I-V) measurements are made on structures where the PureB connects to p-type Si regions. One set of devices comprises ring-shaped structures designed for measuring the conductance through the IHL. In these structures, the PureB layer is deposited in rings that are contacted at the inner and outer perimeter with Al. Another set of samples includes devices where the PureB layer was deposited on p-type bulk Si. At room temperature, a close to linear change of current with voltage was seen irrespective of the PureB layer thickness and post-deposition processing. Lowering the operating temperature led to an increasingly non-linear I-V characteristics. Plausible explanations for the non-linear behavior are considered and discussed in the paper.